: Is my Fantasy YA series idea interesting and unique? For a while now I’ve had an idea for a YA series brewing in my mind. The series takes place in an urban setting much like our world

The concept is good as far as magic goes. Normally, I'd caution against introducing fantastical elements (so, new laws of nature) and breaking the rules, but elemental magic is a staple of fantasy; because it needs no introduction, you can get away with using a cast of characters which are a twist on the trope. The dual-power wielder needs a plot hook, the other characters are already intriguing. I'd read this.

However, other things don't quite make sense:

The series takes place in an urban setting much like our world now

A setting in which people have personal magical powers is definitely not "much like our world" - ours is dependent on large-scale labor organization. The ability to direct massed efforts matters the most, and, in turn, these leaders rely on the cooperation and obedience of workers. A world in which some people are not beholden to community norms would be built differently.
Magic would drive technological development in a different direction, which will, of course, product a society substantially dissimilar from ours. Settlements are often founded along rivers, which served as a water supply and a means of transporting goods; everything changes if people can fly or summon rain on demand.

plenty of illegal arenas exist where people duel each other in high-stake battles

Right now in the real world, there exist cock-fights and dog-fights and bull-fights and Most Dangerous Game hunts. Those aren't remotely as high-stakes as the stock market or the illegal weapons trade. If you want to have fights truly high-stakes, you need to make them legal and build your world around them, like in Pokemon or Beyblade.
Look up the murder rate in a real modern society that is the basis of your setting - chances are it's so low it can't possibly account for the deaths from all the illegal duels that are going on. High crime rates break communities and send people to look for asylum elsewhere.
Most people in a modern society would opt to go on welfare rather than risk death or maiming on the regular.

a person is given a selection of jobs by the government to choose from that are suited to it - for example, a Water may be a firefighter, and a Fire may be a blacksmith

Modern governments do not assign jobs on an individual basis, one reason being they are too reliant on social contract to employ what is essentially forced labor. Pre-modern governments would not have the infrastructure for it, considering the increased personal autonomy which comes with wielding magic. In a world with a semblance of civil rights, having particular elemental magic would be, instead, a job requirement.
And there's the tech level dissonance: dedicated firefighters are an extremely recent, urban phenomenon, and modern blacksmiths are artists.

I am not familiar with The Darkest Minds, but from looking at the Wikipedia page, your premise has nothing in common with it. In that series, the magic is not integrated into society, but is apparently wielded only by children, a horizontal slice of it. The children are, absurdly, oppressed by the (soon-to-be-extinct) United States of Evil Adults, while the rest of the world does nothing to take advantage of US fragility and/or save the tortured children.

Avatar: the Last Airbender has elemental powers. However,

its world is stylized after East and Southeast Asia (a distinguishing feature),
different elementalists belong to different nations (yours is integrated),
power wielders are not privileged over non-wielders or vice versa (you have the dark-eyed boy and the supergirl who wants to share and uplift the powerless),
powers scale linearly (you have the supergirl, again),
powers are, with rare exceptions, not subject to industrial exploitation (yours are),
the plot is a standard road adventure affair with a final boss to defeat.

In conclusion:

The magic system is an excellent choice - it is a good fit for YA and for these characters. Remember that elements are just thematic tags on individual powers. When you think of a cool power, think which element it might belong to by looking at their existing power set and what an elementalist with this power set can do. For example, seeing in the dark - is it a power for Earth (echolocation) or Air (convection) or Fire (infravision)? Look at your power sets, think through the social and plot consequences of assigning it to each group, and choose what's best for the story.

DO NOT invoke real science or scientific concepts. "Can I boil a pot of tea by changing the fine-structure constant?" isn't an answerable question. Messing with the fundamental laws of real physics has far-reaching consequences which destroy the whole fictional reality. A good resource which handily demonstrates the inherent absurdities is Randall Munroe's What If.

If you want different names/concepts for power groups, look at historical pseudoscience (such as alchemy) and mythology.

Work on worldbuilding. Think about how magic affects technology and how technology affects society. Worldbuilding.SE might be of help refining your ideas.

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This started as a comment, but got awfully long.

Your premise bears a lot of resemblance to the world of Avatar: The Last Airbender.

"Each human has the ability to wield an Element corresponding to their eye colour - blue is Water, brown is Fire, green/hazel is Earth and grey is Air."
While some people can't control any elements at all, those who can "bend" an element only have one of the four, and their eyes are colored accordingly. (Except for the Avatar-- more on this later.)
"Depending on their Element, a person is given a selection of jobs by the government to choose from that are suited to it - for example, a Water may be a firefighter, and a Fire may be a blacksmith." Yes, although jobs aren't imposed by the government. This is explored more in the follow-up series The Legend of Korra, where different benders live in the same city-- firebenders use their lightning to power machinery, earthbenders construct buildings, etc.
"An albino girl who has the rare ability to control Aether, the 'fifth element'" There is a rare fifth element, energy, although it's probably different from what you have in mind. Energybending allows a person to give or take away someone else's ability to bend.
"A regular boy with very dark eyes, often made fun of due to his extremely weak powers." Not everyone can bend at all, so weak or no powers are common. One of the main characters, Sokka, is a nonbender who uses mundane weapons to fight (mostly his trusty boomerang)-- though he's a contributing member of the group, his friends occasionally give him a hard time for being "normal."
"A boy with heterochromia who has the ability to control two elements." While eye color doesn't determine bending ability (it only indicates it), one person, the Avatar, can control all the elements. His eyes have the color of his birth element, but he can learn to bend the others.
"A girl with immense power that turns heads with a burning desire to share it with the weak." Another main character, Katara, is a powerful waterbender who does everything she can to help others. The most head-turning character, though, is the blind girl Toph, who is widely considered the strongest earthbender in the world.

I definitely think your series could be interesting given that your main characters defy the mold of the rest of society in different ways. If you want to avoid similarities, though, try changing your elements-- adding an extra "common" element or two, or using a different four.

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