A few days ago I noticed one chick (she's about 3 weeks old now) had a small bald spot where her wing attaches to the body at the top. I thought it might be because the chicks are starting to get feathers in. But I checked again today and now it seems the bald spot is bigger and looks like it's a bubble (like fluid under it)! Help, what should I do? Sorry it's not a great pic.