Yellow or brown diarrhea? True diarrhea(not just mushy cecals with normal round fecals) is critical and usually an emergency situation, especially in baby rabbits. And with them also not eating, their chances of surviving much longer aren't good, and you may not have the time needed to get things turned around.
They would need to be taken to an experienced rabbit vet immediately, and get put on fluids, metronidazole, questran, and force feedings. You can try switching back to the other formula if you want, but if the diarrhea is from clostridium growth in the digestive tract, switching back over isn't likely to make a difference. It will only help if they have a sensitivity to the goats milk. At this point, I don't think it would hurt to at least try switching back over.
A world-wide list of local rabbit vets near me maintained by House Rabbit Society so that people can find the closest rabbit vet near you.
rabbit.org