Yes, alfalfa is not good at all for rabbits.
Hay with rabbits acts as a digestive/motility stimulant(fiber). They do not pull nutrients such as proteins/carbs from the hay and with calcium, they will pull that in excess which is not good.
A good grass hay is good for gut motility, that is what we want to achieve from the fiber.
You want to treat for cocci/worms, increase the pellets slowly, give grass hay and top dress with calf manna to get the weight on generally speaking.
Check the teeth, because a malocclusion will decrease feed intake. Also check to see how much water they are consuming. Water intake correlates specifically with feed intake.
Stresses, such as weather change, a bird in the barn, a raccoon, a dog barking, a new rabbit placed in a cage next door or a goat rubbing under the cage can cause them to decrease feed intake.