Mate in my area about 5 year ago there were plenty lofts had the same problem with these blood lumps,now all these lofts were feeding different so it was nowt to do with rich feeding.If its the same thing as wee had then i can assure you it does them no harm as my good hen treble 4 had them on her as a yb and came out and scored the next year and then went on to win 1st west section SNFC Alencon 540 mls.Its thought to be some kind of virus that causes it being similar to pox virus so iam told. :