I would certainly try to get them eating creep to replace the protein in the milk they're not getting.
If they eat cake they'll be fine without milk at 2 months.
If they are well-fleshed and will eat creep, it may be better to let them get on with it now.
However, if one will take milk and you don't mind bottle feeding, then personally I
would offer milk for a few weeks, especially if there is any lack of condition there. I'd offer the bottle to the refuser first each time, then feed the one that wants some. Not too much at a time - maybe 250ml three times a day, or up to 300ml twice - not anything like as much as a litre a day, so that he does get on and eat creep. You may find the refuser does decide to like milk after a few days
.
I expect others will give you different advice, but that's what I'd do.