Yes, they sometime eat their own poo. I might suggest that you feed them in a seperate tank. You can keep an eye on them and they are less likely to eat their own poo if they are not hungry. However, that may not be true as they will sometimes get in a feeding frenzy and eat anything during that time. You may have to feed and scoop, feed and scoop. Good Luck!!
My RES started to eat their poop after I had them for about a month and this continued for about 2 months. Just recently though they have stopped eating the poop. Probably because I started giving them for calcium and better lighting and all that stuff. Maybe they just dont see it though..
I noticed my turtle do this for the first time the other day. Nothing to worry about though, other animals do this too, such as rabbits. There are still nutrients in the poo so they eat it, no big deal.
YEP -- These guys will eat almost anything. They will eat their own scutes, their own poop and any rocks they can get in their mouth. Many years ago I put a piece of carpet so they would not scratch their plastron they ate that and got constipated. I did not know until I had to pull it out of their rear end. YES -- almost anything--