Update:
The saddle butterfly is doing well. After about 8 weeks, he finally started eating the food I give them, and now actually eagerly competes with the trigger for the pieces. The spot that was on his front fin went away on its own, so I guess maybe it was lymphocystis? Whatever, he seems to be doing very well. I should have taken before/after pictures of the aptasia, because he's really gotten that under control.
However....
I noticed my Valentini puffer flashing against the rocks a few times. I couldn't see anything apparently wrong, but then I noticed that right in front of his front fin on one side, it looks like a bubble inflating and deflating as he breathes (I guess it's his gill). It is very tiny and hard to see, but the other side has no bubble. It just looks like an open... well, gill.
So now I'm wondering if it is a gill fluke? Maybe I
should have treated the tank, but the butterfly got better. The puffer is pretty old though I think, maybe he's just more susceptible. There is no way I can start treatment now, as I'm going away for a week and the neighbour kid is coming in to take care of the critters. She's pretty reliable, but no way I'm leaving her to medicate. I don't even know for sure what/if I should medicate. Any thoughts???