The buck's weights seems okay, but since it looks like his eye might be involved - another symptom of
E. cuniculi - I'd start the buck on Safeguard (fenbendazole) paste, a very small pea-sized blob in his mouth. Rabbits often like it, as it's apple-flavored. But if he resists, you can just smear it on his mouth and inside his front legs and he'll groom it off and ingest it that way. I've not had a lot of luck with curing bucks but sine he's still with you he might come around. I know
@RabbitsOfTheCreek has a little buck that has lived quite a long time with pretty severe head tilt. But I'd try fenbendazole just the same, since it might help, and I've not heard of it hurting a rabbit.
The doe looks like she might be in pretty dire straits. I don't see a huge coccidiosis belly, and I can't tell from the photo what the issue is with her stomach, but that is one thin bunny, way too emaciated to be explained just by nursing kits (and that wouldn't cause a messy tail). If possible I'd get her on Benebac or another probiotic, even try plain yogurt with no additives if you can't find an herbivore probiotic gel or paste. I'd also supplement her with Critical Care, which is a powdered nutritional aid you can often find in pet stores. When rabbits are off their feed, they sometimes don't want to eat it, so you can try mixing it up pretty thinly and putting small amounts at a time in her mouth with a syringe. I'd also offer her anything you know she likes or might like - sunflower seeds, bits of apple, fresh grass or kale, chickweed, dandelion leaves or flowers, wild plantain -
anything to get her eating again. If you have access to willow bushes or willow trees, gave her several branches with leaves; willows have a substance that is a natural pain-killer and rabbits can use them to self-medicate. I wouldn't necessarily take her bunnies away, but make sure they have hay, pellets and fresh clean water they can reach, since this doe probably isn't providing a whole lot in terms of nutrition for them at this point.
You said she has a messy tail - is it diarrhea (dark brown and super liquidy, all over the cage) or is it perhaps uneaten cecotropes, or just lack of cleaning? Is her belly hot where it's bulging, or is there a hard lump somewhere, or is it soft and just sagging? Can you tell if she's eating or drinking at all?
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