Help- Frog won't eat

[Gesteur]

I have 3 auratus in a 18x18x24 which were doing great until recently 1 of the 3 frogs isn't really eating much and is getting thin/weak. Should I separate them? It does not seem like either of the other 2 frogs are bullying him, even though I have seen all three of them walk over one another before. They are all only about 7-8 months old. I have another tank to put him in but worried that the move might stress him out so he doesn't eat due to that.

[Philsuma]

I would seperate the thin frog right away - place it in it's own enclosure.

Could be stress or disease.