L022 Gold Spot Pleco Wound - Gotten worse! Please advise

Tank

What is the water volume of the tank? 125 gallons
How long has the tank been running? about 2 years
Does it have a filter? It has 3: An FX4, A big sponge filter and an emperor bio wheel
Does it have a heater? It has 2 with a heat controller at 78
What is the water temperature? 77-79 degrees
What is the entire stocking of this tank? (Please list all fish and inverts.)
7 Silver Dollars
8 Yoyo loaches
1 l022 pleco
7 Denison Barbs

Maintenance
How often do you change the water? Once weekly
How much of the water do you change? 30-40%
What do you use to treat your water? Prime
Do you vacuum the substrate or just the water? Both

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? API freshwater master kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.

Ammonia: 0
Nitrite:0
Nitrate:20
pH: 7.8

Feeding
How often do you feed your fish? Once a day
How much do you feed your fish? This is difficult to answer. I add some floating flakes for the denisons, usually a bit because they fight over it with the yoyo's. I add in some wafers for the pleco and silver dollars and some sinking pellets for the yoyo's. Once a week I feed bloodworms, romaine lettuce and zucchinI for the herbivores
What brand of food do you feed your fish? NLS pellets, Omega one flakes, HikarI wafers, Wardley Shrimp pellets
Do you feed frozen or freeze-dried foods? Frozen bloodworms once a week

Illness & Symptoms
How long have you had this fish? ~2 years
How long ago did you first notice these symptoms? Just today
In a few words, can you explain the symptoms? What looks like a wound on the one side of his body. Other side has something similar and what looks like a bubble forming off the skin (blister maybe?) I couldn't get good photos of that as he wouldn't turn for me, but I will try to again later.
Have you started any treatment for the illness? No
Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all? He seems to sit out in the open a little more than usual, doing that weird thing where he just kind of .... hovers in the water somehow. He's always done this a little bit though.
The biggest change I've made is replacing their light with a shoplight that is much brighter, a day or two ago now. nothing else has changed.

Any advice would be appreciated. He seems to maybe be bloated in these pictures? I'm unsure. He's always been a chonker. But whatever this is looks nasty and painful

 

Addendum : I'm wondering if this might not be caused by decorations? My pleco likes to go inside of some fake coral and rock, and I've noticed as he's gotten bigger, he's had more trouble fitting. I figured when he got too big he'd use the pvc pipe and fake log I put in there. Could this be from him forcing himself into holes?

 

I'm going to remove the troublesome decorations today and see if that may be the cause. There's too many diseases that mention white puffy things, I think I better stop doing research >.<

 

I think my pleco is seriously sick. He looks very bloated, way more than yesterday and cannot seem to move well. If anyone can help, please do!

Could this be columnaris?

 

Update, mostly to keep me sane :

I dosed kanaplex for three days and there was no change. Nitrates were higher than normal and I discovered my nephew had been feeding when I wasn't looking. Sigh.

So I did huge water changes, enough to cause bubbles and have nitrates back under control. Another fish, a denison I think had a prolapse a while back, had dropsy likely due to water quality, ugh, and was so far along I ended up putting him down. I think nitrates and some rogue bacteria were the cause here.

The pleco still swims around, though not well. Still bloated, but I'm assuming that the kanaplex may have killed the bacteria and he just hasn't expelled fluid yet? Hopefully.

I'm starting daily Epsom salt baths now, will do another water change tomorrow and closely monitor my nephew and the water quality. Also planning on building a sump and trying to get more floating plants in there (silver dollars haven't been devouring guppy grass as far as I can tell).

I'm hoping his condition improves. No other fish are showing signs of bloat or dropsy at the moment, but I'll keep monitoring. Here's hoping the sump and plants will greatly improve my filtering and water chemistry so I can't be sabotaged again. (Kidding kinda)