I am no Tarantula expert but sounds to me like its just getting used to its new environment...Also a few days of not eating isn't much of a worry with T's. I had half inch spiders not eat for weeks and it was fine. Though once I did get a good supply of flightless fruitflies (as i couldn't find any small enough crickets at local pet stores..smallest I could get were same size of the spiderling or better) Once I had the fruitflies, it grew steadily...But he did spend most of a winter eating very little...