Hi!
how old is Snooky? Pellets will often times make the bunny become dehydrated if a lot are given since they do not have water in them. She needs to be seen by a rabbit savvy vet because if a bunny becomes dehydrated, they can go into stasis and it seems like maybe she is starting it. Has she been pooping regularly? Still active and eating her favorite treats(in moderation)? Pellets are known to cause molar spurs in Lops( Snooky is a lop right? And that can cause them to go into pain stop eating.
I hope this helps

I get that the vet wants her to gain weight but since her poops are getting smaller, I am concerned she might be going into stasis.

Keep giving her as much veggies as you can to get her hydrated and stop the pellets for half a day or so until she starts pooping normally. If she doesn’t, I would call the vet and say what she is doing and she might need to be seen. Just make sure she doesn’t start showing any abnormal signs and she should be fine!