For the record, my salifin from CF (was feeding on pellets there) took 1.5 months before it started to eat anything.
My AT took around 1.5 months before it starts on nori and finally after nearly 4 months started on pellets.
My yellow tang (also from CF) took ard 1 months befor it started to feed.
During the time that they have not accept prepared food, they should be fine with just pecking on the LR.
If you had lots of LR with algae on it for it to peck then it should be fine.