I bought 4 guppies plus a sword a little less than a month ago and added them to my 10 gallon. We just came back from a week long vacation and one of the white guppies looked severally underfed. The 2 of the fish had big bellies and the other one looked normal. The next morning that white guppy was dead, and now one of the other ones is not looking good. The other guppies keep harassing him. What should I do? They were fine before this. Please HELP!!