Pooping in bowls can often be caused by a few things and corrected a few different ways depending on the set up you have, without more information or photos of your particular set up it is going to be hard to offer you any ideas or help to sort the issue out.
I put the food bowl high up and in a corner so it's hard to perch on it. Then the water bowl I had the same but somehow still poop. Well I bought a little water dispenser I was going to try. I attached it on top of the water bowl. So they learn it has water but can still get water from the bowl. Well it also makes it an impossible perch. Don't know why birds enjoy using them that way. Seems awkward but I'm no bird. In any event try and see if there is a way to make the water bowl un friendly for perching. Maybe a toy or something blocking part? Thats my plan b