Crop issues in 4 week old pullet

I have a 4 week old pullet. The hatching eggs I bought were said to be Black Copper Marans, but this bird is definitely some sort of barnyard mix. No matter. A few days ago (4 days, perhaps?), I was moving my chicks out of the brooder for cleaning and I noticed that one of them had some foamy stuff coming out of its mouth. Later, as I transferred the chicks back into the brooder I noticed that one chick had a slightly squishy chest, but I didn't think much of it. Yesterday, it became apparent that it was the same bird with both of these issues and a quick google search suggests that it is a crop issue. My chicks have only been given chick starter, grit, and water at this point, so if impaction is the issue, I suspect that the wood shavings in the brooder would be to blame. This morning I isolated the pullet with only grit and water with ACV. Her crop is squishy and large (about the size of an egg on a 4 week old bird) and and it hasn't changed size at all since being isolated. I did some light massage on the crop and some mashed up food came up. Shortly afterwards, the bird pooped for the first time all day, which makes me hopeful that some gut motility is happening. All things considered, the bird seems pretty alert and healthy, but she keeps doing the head bobbing, neck extending thing, that looks like she's trying to regurgitate or swallow or something. I see so many different ideas about how to approach this situation. I'm nervous to massage too vigorous and risk aspiration, and I also worry about depriving her of food for too long. I welcome any advice.