Black Comb lumps

[Sidewinder]

My egg productions has gone down, and I've noticed a few of my hens have started showing up with black lumps on their combs, could this be part of the problem and what has caused it? I gave them a couple lemons about a week ago that has been the only thing out of the ordinary for the girls, other that one of them going broody. I don't know what is going on they are a young flock of 9 hens about 8 months old.

 

[debid]

Fowl pox?

http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/204801.htm