I am running a kicker 2500.1 on a custom built Fi btl 18 in a box built to Fi specs. I have a xs power 3100 as my second battery. When I first hooked everything up my amp gain was maybe 1/4 of the way up and it sounded great. Now it's like the amp is losing power I had to turn the gain up more just to get it to sound like it did when I first hooked it up and truthfully the power still isn't there like it was at first... What could it be.