I got 4 kicker cvr 12's all in a sealed box 400 rms each and a hifonics brutus brz1700.1D mono block?

hi im having problems with my system i have 4 cvr 12's they are all dual 2 ohm's each are wired to one ohm I hifonics BRZ1700.1D and a Kinetik 600 and i have 6 guage power wire and 4 gauge ground wire they are temporary i have the bass boost at 75% and the low pass is 20% and gain is at 65% when i turn the volume up a little the bass goes down is it because of the size power wire or the ohm load.and if i hook the subs voice coils in series would they receive less power than if they were in parallel. how should i wire them for the most power oh and i have a 120 amp alt