> Guess my question would be is there anything else I can do to have my salary up to the level's minimum? I don't think in the legal sense there is anything (back pay, etc..) but it just seems a little unethical to me

You should handle this situation like any other raise negotiation; You tell your manager that you want an interview to discuss your salary. You explain that you have gained achievements _y_ and you've reflected experience _x_ at work and that you wish to receive a raise of _z%_ which is _u%_ from the market's average, based on a research which you should always do before a interview as such.

There's nothing unethical about you having a lower salary than someone else since you haven't requested a raise before; you wouldn't find it unethical for someone else to have a lower salary than you if that individual never asked for a higher salary.

Don't concentrate too much on your coworkers, focus on _your skills_ and use them to get the raise you're looking for, just remember that _you have to ask for it_, no one is going to give you a raise _just because_.

[Recommended reading material](http://workplace.stackexchange.com/questions/1025/how-should-i-properly-approach-my-boss-if-im-feeling-underpaid).