Hey there, for others who are having specific issues I'm sorry but I can't help there, I'm pretty new to this too. But I wanted to leave a note and say that this is really helpful for me -- we have one chicken who has been having problems lately. She just suddenly couldn't walk. At first we thought it was Marek's disease but for one, my husband remembered that there was a loud squawk in their coop the night before she suddenly couldn't walk, and for another she's been walking really well the last day and it's only been two days that she wasn't walking well. We are hoping she just fell off of her roost or sprained her leg somehow.
Long story short (too late?) because we thought it was Marerk's, she's been in isolation in a smaller cage and my husband noticed this huge lump on her chest. I think this thread answered it -- the lump has been there for at least 24 hours but it's soft and she hasn't had anything to do in her small isolation cage other than eat and drink, so my guess is that her crop is just really full from her having nothing to do other than sleep, eat and drink. We are going to take away her food tonight and give it back to her tomorrow in the late morning, and see if that helps.
FYI we are going to keep her in isolation a bit longer until we are sure it was just a sprain. Still could be Marek's but we are really hopeful. My understanding too is that if it's Marek's our other girls are already contaminated, but it sounds like isolation is always a good first reaction when you're not sure.