I just want to say i am 16 and have only been keeping fish for about 2 years and not 100 percent certain on how everything works yet so i have smallish 48l tank which only has two angel fish and a fairly small pleco. I also have a bigger 58l tank which is currently housing one fairly big bristlenose pleco which i have had take from my brother because he was struggling to keep up with the tank and a day before i went to collect the fish he thinks the pleco got a heater burn because he started to notice he was sitting behind it for quite a long time and even though he tried moving him he wouldn’t budge. i am posting because i am unsure what to do in the long run and to see if it is burn or not and whether or not it looks like it could be treated and what to treat it with. Have attached a photo of the whole tank and the pleco up close it isn’t fully white and has a few red specks on the outer edge.