This is my first time with ducklings and everything seemed to be going great until I checked on them today. There are 8 Call ducklings in a pen outside with about 4-5 of them with bloody wing feathers. I separated two that I noticed constantly picking on the others.

The last time I checked on them was this morning and they were perfectly fine. My mom and I put some Rooster-no-pick paste on their wings to discourage further picking, but should I be doing something else? I can't see them being crowded and I've had larger chicks in there before without any problems. I recently changed feed though from Chick starter to Layer crumbles. The Layer crumbles have 16% protein in them. Any ideas as to the cause of the problem?

Oh, and they are about 4 weeks old.