I was using ceramic bowls. I just tried to keep my ducklings' feet drier and cleaner and it went away. At this age they're producing so much poop and causing such a mess with the water that it's hard.
Mine also tried to eat any bedding I tried using so I switched to washable puppy pads which...
I've seen those cuts with some of my ducklings in the past, I thought they were from standing on wet bedding/surfaces too much, although I wasn't really sure. I wasn't using anything sharp like shavings. It didn't look normal to me.