Ugly spot near tail feathers

[jjfab]

I have four Australops that are 5-6 weeks old. They are almost fully feathered. Two look great. The other two have ugly spots at the base of their tails. Pictures are below. At first I thought this was just the last area where feathers are growing in, but I'm becoming concerned that it could be a skin condition or that they are being pecked by the other birds (I do not see any signs of aggression when I'm looking at them). Any ideas?

 

[pgpoultry]

It's the preening (oil) gland , where chickens take oil to keep their feathers in good condition. The feathers around it will grow in, but there will be a raised oil gland in the middle. Don't worry.