Ok so I have two tens powered by a jl 500/1. My problem is that I go to drive the car today (first time in 4 or so days) and the subs are acting up. First they came on and off intermittenly, then once they came on full time, they are significantly less loud then before. I have a few theorys
-Stock Battery on its last legs (my lights are dimming like crazy
-Bad power/ground connection
-RCA problem (unplugged, shorting out etc)
-Blown Sub
-Bad Connection in Sub wiring

Any thoughts or opinions?

Sounds like something shorted or cam loose somewhere. I'd check all the wiring first, since that's the easiest thing to do. Your amp might also have a problem (grounding or otherwise).