Sounds like the calf had something else going on. I have raised bucket calves many times. Went out of the cattle business a few years ago. I don't think taking it away too soon was the problem as I have raised several that the mama died or rejected . Hopefully the other two are doing fine. I had a colt one time this happened to we did IV's and everything. vet did some testing for his own curiosity ,pato came back e-cloi he was just two days old ,you just never know.