I am having this same issue and have not been able to find any advice anywhere on the entire Internet or the 10 books from the library.
All of my 13 chicks developed mud balls on their feet after I introduced a new mix of soil scratch, I keep it by the water and now that they are 3 weeks old they spill the water alot and made mud apparently. So I don't know how many days they have had this, the new dirt mix has been in there 5 days, they weren't acting like they noticed the balls at all. but I saw it yesterday and removed the mud balls, some of them after softening in water for a few minutes and some chipping it off til they popped off, with scissors .
at least 4 birds had a couple, (1 to 3 per bird) nails come off with the mud ball, I did not pull them off hard or anything.
Maybe about 7 or 8 at the most, nails were lost, 2 bled just a little, the others didnt bleed at all. it looks like maybe the nail deteriorated or rotted under the mud? But they don't look like the toes are rotted or infected at all. They just popped off with the mud!
Also these are bantams, 3 weeks old from
tractor supply, I have no idea what kind except they are brown with fuzzy feet. The other 2 kinds of bantams I have and 3 easter Eggers all had mud balls too but their toe nails were fine after i removed them. Only the 5 brown bantams lost nails.