When I first got Mishka and Laska, they were fed solely Marshalls ferret food. Over the past few weeks, I've been mixing that with Wellness Core Kitten, which they both seem to like more. We got past the initial first weird poops, and then things got normal. The past few days though, Laska's poops have been a little thin and greenish. Energy-wise, she's been fine - Not lethargic, running around everywhere. No sneezing (not any more so than usual), no runny nose/eyes. Everything else is perfectly normal, except her poop. Any reason to be concerned? Or is just something that will work itself out?

What about treats?  Any new treats or given too much treats?

Keep eye on your little one.

Treats are actually really infrequent - Maybe once or twice a week. Nothing else seems to be off except that. Any guesses what could cause it?

Maybe she just has upset tummy.  I would just keep close eye on the little one.
You might want to check any toys, that she  may of chew on or got hold of something.  Check those spots where  they hide their toys.

I hope this helps