Feather loss in 9 week olds

[Gbear74]

I have a group of 9 week olds and a group of 4 week olds, both are losing feathers. Not all are affected and some have mild loss while others are naked around neck on back and around vent. There are no sores or blisters. Not even any visible rash, just naked skin. My question is, do young chickens moult or is it normal for them to have feather loss?

I can't post pics on here yet but I can email if anyone thinks they can help with this.

 

[Gbear74]

I found a couple of blister type things on them today. I seems that the blisters are full of air not puss or water. Some of them do have a dark runny poo also. Could this be Meraks?

 

[Haunted55]

Does it look anything like the pictures in this thread?

https://www.backyardchickens.com/t/763930/please-look-at-these-pictures-and-help-us