Fish drama

I have two big and one small tank for fish. In one, I have the Fish Horde, which consists of three mollies and, until a couple of days ago, two platy fish. All but Harry, a black-finned platy, are about the same size. Harry is smaller. He was darting around with the rest of them until a couple of days ago and I got worried so I started watching closely, and he was spending all his time hiding behind a big plant. He didn't come out to eat. He didn't come out to play tag, which is their favorite thing. I'd check on him and he'd come out and dart around to get away from me, but as soon as I backed off, back in the corner he went. I decided the others were picking on him but was kind of at a loss as to what to do. Freckles the new betta has a tiny tank, which is okay for him alone, but not big enough to share. And Opie the other betta has had a 10 gallon tank to himself (he shares with a plethora of snails, but they're not what you would call interactive, LOL) for months and months. But that was the only option, so I fished Harry out of the Horde's domicile and carried him over to Opie's tank and put him in. The temp and conditions are identical, so I didn't worry about it shocking his system. He started swimming around checking it out, Opie finally noticed him and started following him around, but didn't nip at him, just stared and followed. I kept a close eye on them that evening and Opie lost interest and went back to his usual non-activity while Harry cruised around meeting the snails and trying out the hideys. Every now and then Opie would come out and follow Harry around a while, but neither fish was in any hurry and they just sort of moseyed around. It's been that way for a couple of days now and Harry isn't hiding, though there are plenty of places to do so in that tank. Opie either has severe short term memory loss or he just finds it amusing to follow Harry around for a while a few times a day. So I THINK it's a successful move. Opie is really lazy and spends most of his time hanging out next to the heater or in his floating log and only shows any real energy when it's time to eat, so having a roommate to encourage him to swim around and do something is probably good for him, and I'm hoping that Harry is happy in there without the Horde chasing him so he has to go hide out in the corner all the time. They say you should keep platies in schools, but Harry might be the exception to that rule.