Why are my chicks loosing their feathers?

[JollyMonster]

I have 50 straight run chicks and 9 straight run turkeys that are penned together. They are currently 5 weeks old. They've been doing great together! I know I'll need to separate them soon due to have fast turkeys grow.
I've noticed some of my chicks are loosing their feathers. Are they old enough to be molting? Are the roos old enough to be mounting? The turkeys, as far as I can tell are not picking on them. Is it mites? What do I do? How do I fix this? If ivermectin is needed, what kind and where do I got it?

 

[FrostRanger]

Chicks go through several juvenile molts, totally normal and this won't be the last one

 

[rosemarythyme]

Chicks have juvenile molts but that looks like picking damage on bird 1. Bird 2 is harder to tell what's going on... slower feathering cockerel with maybe picking on the back end?

50 chicks need a LOT of room and stuff to do to keep them from turning on each other.