Is it eating well? Are you sure this isn't just a color pattern change? Plecos are notorious for this although I've never kept this particular species. Most of the "fungus" cases are bacterial. Fungal infections are very rare and yours is certainly not fungal.
I feed him algea wafers and shrimp pellets. I feed the other fish flakes, frozen bloodworms, and brine shrimp so he may get some of that too. I also have driftwood.
diet can cause pigment change along with water parameters just about anything even just a natural occourance sometimes I wouldnt be worried just yet
still looks very healthy