I just bought my hamsters about a week ago, (dont worry, i keep them monitered closely, they've lived together for months now) and I've noticed that they sometimes are more active during the day than at night, and vice versa. I'm kind of worried... They seem to have settled in nicely though, within an hour of bringing them home they ate and ran on the wheel. It's probably nothing, but Ive been having some pet troubles and I just want to make sure