Do the lump look fluffy, also do they resemble a cauliflower hard to see in the pic.
Not fluffy (fungus), and not cauliflower-like. Just sort of a smooth lump.
But guess what.....now it's gone!
Update:
I did some construction work in the tank today (replaced some of the gravel that contained shell bits, with plain gravel, to bring the pH down from 7.5 toward neutral or lower). The pleco went pale all over, while I was disturbing his home....to be expected with any fish, healthy or not.
This evening, I gave him a bit of Aquarian Algae Eater sinking Algae Chips, followed by some pea. Now his belly is swollen again, so I think he has been having a reaction to that brand of wafer. Aquarian has 3 forms of wheat, plus rice, plus soybean, in its first 6 ingredients. I've just read that some fish have bad reactions to soy. I also doubt that his system has ever had wheat or rice, since those plants don't grow in the South American jungle!
I'll stop feeding him that brand of wafer. I'm going back to Hikari Tropical Algae Wafers (which have no soy, and less wheat), alternating with peas. I'll see how he looks after a couple of days on that. I also have some Omega One sinking wafers, that have kelp, spirulina, salmon, cod, herring, and other seafoods as their top 6 ingredients.
He still has that pale area, but I'm now thinking that KathyM is right, about it being just stress, since he doesn't act sick at all.
P.S. KathyM, isn't it amazing the shots those digital cameras take? I just have an entry-level one, and I'm no photographer! It even shows how scratched up my aquarium glass is!