I've got some female guppies in isolation, even though I see some of them could be pregnant. When I spot a really huge belly, I usually put her in a hatchery so she can safely deliver. Problem is, each time I isolate the female, she seems to pine for her friends and after a few days alone, she died. This has been happening twice and its made me very wary of isolating them now.

Why does this happen? I thought they'll be more confident on their own to drop.