How long ago is "just stopped eating?" If they're suddenly getting thin I would suspect internal parasites. I would get fecals done by a vet for the both of them to be sure. If it's not parasites then it may be stress. Once they're seperated things might pick up.

I only feed crickets to mine and he does very well on them. He's coming off a winter fast in which he dropped nearly 30 grams. Last fall he weighed around 95 grams and dropped down to about 67 over winter. He's been eating good again for about three weeks now and has gained back about 10 of that already.

Quig