We got two goldfish about three weeks ago. I have noticed one picks on the other by pushing him out of the way, following him and gulping at his body. He seemed to be okay the first couple of weeks. But recently I noticed the picked on one has been staying on the bottom of the tank most of the time and not really swimming. Also when he tries to eat, the food will come back out of his mouth and he tries to eat it again but it doesn't stay inside. What are some thoughts on this and suggestions?