She is about four weeks old, is smaller then the other two, and has this ginormous squishy chest. Have been hand feeding her for a few days now, making sure the others aren't keeping her from food and water. She acts pretty normal, what could it be???
Aw, poor thing. Actually the large squishy chest is probably a partially blocked crop. Sometimes grass or even bedding can block the crop. If you go for a couple hours without feeding her and the chest size does not go down, then that is the most likely cause. The first step is to massage her chest to try to break up the blockage. This link includes treatment information if you scroll down : https://www.backyardchickens.com/t/517234/medical-treatments-recommended-by-bycers#post_6580204
(I think most people start with the olive oil and vinegar first. Using copper sulfate is not as common)
Do a search on "impacted crop" or "sour crop" to get more information.