Always Something!!

Ok, let me start by saying I appreciate any and all help!

I have 2 Cvx 15's powered by 2 Kicker 750.1's. 1 Kinetik 1400 Battery 2 Kicker 6x9's running off Hu. and 2 Kicker 6.5's running off Hu. (also another pair of 6.5's and a pair of 4x6 all kicker but currently not wired up)

The Problem I'm running into all of a sudden is, with both gains above half way, both subs sound dampened or producing 1/4 the power with nearly no sound quality coming from them. Although, if you turn one of either two amps below half way you can hear the opposite sub start producing bass/sound, at a dampened yet more noticeable sound then when full powered.
Sorry if not too clear just trying to explain what im hearing and how/when.
I've checked Hu. ground, both amps ground and power, also checked the RCA's and speaker wires, the batteries power and ground, checked the sub's and their wiring.!!
Seemed to start the same day I removed a sub to add some wood corking in the screw holes to keep the sub screwed in better which was yesterday.

Any questions you ask I will surely try and respond as quickly as possible, always something I swear.

one sub is wired out of phase from the other.

Thought so also because this is what its sounding like but I didn't rewire the subs nor are the wires loose... woofers are less then 2-3 months old amps maybe 4-5 months. Nothing seems wrong with either set when turning one down and the other up, so i don't think it is a coil issue.

Appreciate the fast response!.

Pull all the speaker wire from the woofers and re-wire them. After doing so, report back.

In the process of removing my other sub in which I had a box terminal along with cheap speaker wire melt on me about a week ago.
I realized my + / - was switched at terminal on the inside!
Of course something easily looked over that was so simple.
Drill battery died before I could check the woofer earlier.
And remember America DIY don't take the help of a dumb *** friend especially at night while their blindness could result in your system FUC*ING UP!

I truly appreciate the time and effort and I promise this won't be my last post! haha. (Was thinking why wouldn't of the polarity difference made an effect until now?)
For a week + I was slumping only started as soon as I removed the opposite sub. Maybe a wire was loose in box?? IdK strange. BUT! as of now all system's a Go! [FIXED]