Control the hay intake......
I would feed them milk, if you want to cut back, milk once a day...
But to cut the milk, as I said before, they have to be eating the right amount of pellet, read all the milk and pellet packs info...
I had a 20% protein starter, it reqd at least 2lbs + a day before you could start cutting milk.
Remember, the hay is to only get rumen working, nutrition must come from milk or pellet at that age.
Cut the hay before anything else.
Try this.
Milk in morning early, nothing else in pen but pellets and water, can put some chaffed hay in with pellet to lead them to eat that, you must measure the amount of pellet and milk, so you know what each is getting, nothing else till night, which would be milk & you can give them a handful of hay then.....
So they then have no choice on what to eat.
Go back to 101, what would a calf that age be doing if with mumma ? The only reason to move them to pellet, it is a darn sight cheaper, well, here it is....otherwise...milky time
Stop thinking of them as weaners...lol