My maltese puppy is losing hair. . . why?

Hello! I just adopted a 13wk old puppy. He has lost some hair around his eyes, and on the tip of his tail. The animal clinic said that he wasn't eating very well (if at all) when he first came. They kept him an extra two weeks, after we officially adopted him. We have him home now, and he's eating fine. We've been feeding him, Before Grain Ground Buffalo(he won't eat solid food) mixed with some NutraCal, steamed carrots, and a little bit of pureed pumpkin. He eats about 3-4x a day. We took him to the vet, and the vet gave us some fish oil tablets to give him 2x a day, this will help his coat the vet said. The vet also said he didn't see any other problems with him, and that we just need to be patient. However, he's been loosing more hair since we've had him, which has been a week. It's only along his tail and around his eyes. I'm worried about him, any suggestions anyone? Has anyone experienced anything similar? Thanks!