This 7 1/2 week old chicks was totally normal yesterday, but this afternoon when I went to let the chicks into the garden, I noticed she couldn't walk very well. I brought her inside to rest and when I took her out this evening noticed two odd bumps when petting her. The tops of her legs are jutting out through her back feathers (see all 3 pics - the last one is the most obvious). side view of 1 of the bumps: This pic shows both bumps (legs jutting out the top): When she stands, her back looks normal, but she is quite wobbly when she walks. I've never seen this before - it's very strange and disconcerting to look at. I don't believe she has Marek's -- she's very young and has not been anywhere near our adult chickens (besides the fact that none of my adults have ever had it) and there are no wild birds that get into their pen. I was thinking she may have injured herself, but am unsure as to how she could have. The only thing out of the ordinary that I can think of is a change of feed yesterday. I've raised all my previous batches of chicks on Purina Start-n-Grow and started these 15 chicks on it also. I switched them a few weeks ago to Manna Pro, which is a much finer crumble. They liked it just as much as the Purina. Yesterday, we went and picked up another bag of Purina starter crumbles because it was more convenient (the store with Manna Pro is much farther from us). The chicks did not like the change. They have hardly eaten any of it for the past two days (yesterday and today). I kept thinking they'd get hungry and figure it out - it's served up in the same feeder and they used to eat when they were even smaller, but to no avail. This evening I wet it down into mash and they did eat some of that. Could this have caused a leg problem in one of my chicks? Not eating much for two days? They do eat some bugs and grass in the afternoons and ate the last of the Manno Pro yesterday morning. Until yesterday, when they didn't eat much, the chicks' diet consisted only of starter feed 24/7, a bit of grass, etc in the afternoons, and apple cider vinegar in their water.