If they died right away (rather than after a few weeks of nursing) then you can rebreed mom right away. Pregnancy doesn't take nearly as much out of the doe as nursing does. So when the kits die right away, it's fine to rebreed mom right away - won't impact her health at all. If she nurses for a few weeks first, then wait a few days to a week or so. If she nurses to weaning, wait a couple weeks ideally.
we've been having TERRIBLE luck with babies this year! we've been raising them for 12 years but i guess there's just some things you cna't explain like how some years moms just cant seem to keep them alive. u can rebreed in a weekish depending on condition