key caps look melted?

I have an Inspiron 15R (5110) and a few of my keys look almost as though they've melted. Now, I work online so I work on this thing 6 days a week and play on it when I'm done working, so I'm really using it 7 days a week from 7am until 10pm or later. That said, most of the keys used most frequently are just shiny, as expected, but the E key has strange lines in it as if it were clawed with a fork or something, the S has half the paint missing from the letter itself, and the A looks outright melted on the edge of the top of the key. It's that A which has me concerned since the "melted" looking part of the key isn't where my finger hits but is along the top edge of the key. I can't figure out what's happening or, more importantly, how to stop it from getting worse. Is it possible that it's overheating and melting from underneath? Is it possible to replace key caps on a laptop keyboard like you can on a traditional keyboard?