You said that it was a small plec.. I have one and he is a butterfly plecostomus and he is my favourite fish, but you have to be real patient to see him as he likes to hide under the treasure chest I have in the corner of my tank.
He likes to eat algae but I also feed him a dedicated plec disc food.. That is what it says on the tin, because he's only small I buy the smallest tub I can and after about six months of being open you really ought to throw it away and buy new as it loses its goodness. This in turn leads to him producing more waste.
I also noticed he doesn't generally eat all the food so i vaccum the gravel pretty regularly too.
Anyway back to your question..
No i don't think your plec has eaten the other fish as he is a vegetarian!!
Happy fish Keeping...
He likes to eat algae but I also feed him a dedicated plec disc food.. That is what it says on the tin, because he's only small I buy the smallest tub I can and after about six months of being open you really ought to throw it away and buy new as it loses its goodness. This in turn leads to him producing more waste.
I also noticed he doesn't generally eat all the food so i vaccum the gravel pretty regularly too.
Anyway back to your question..
No i don't think your plec has eaten the other fish as he is a vegetarian!!
Happy fish Keeping...