Their metabolism is increased, which causes them to eat more, which causes them to poop more. So, warm water would cause this, though, I'm not sure to what degree -- I mean, I'm not sure how noticeable it would really be. They poop so much already.
I've seen that before in almost every pleco I've ever had, seems fairly common but I wouldn't worry about the Plecos. They're just little machines lol.