Okay so I put Merlin and Fishy in the same tank, the on that I divided into 3. Turns out Merlins a sneaky little butt head and somehow made it over to Fishy's side! Fishy is missing a nice piece of his back fin and there's damage to the others. I took Fishy out and put him in the bowl with some betta fix. I'll treat him with some JFE eventually too. I lowered the water levels and checked the dividers. The only way I can think that Merlin got to him was because the water level in the tank was high. Any advice?? Here's some pics.
He almost looks like a double tail now.