Hi I have a four week old black chick that we got from tsc when he was little. he has a few other friends but lately he has been eating a lot more and more tired. he has this lump by the end of his neck and it is kind of squishy. We feed them Sprout chick starter feed, they have fresh water that we change 2-3 times a day and have two heat lamps. I am worried for him, but also another two that have the same issue, but theirs are not as big. their poop has been more on the diarrhea side. I have been mixing sand with their food and they all love it. What could be wrong? I also live right by downtown Chicago so vets that treat chickens are not that common around here. If you need pics let me know.