Rabbits aren’t ever really “too young” to litter train. By the time they’re 8 weeks or so, most DO potty in one area… BUT the habits do tend to get a little sloppy as they get older (3-4 months) and the hormones come into play. Neutering will usually get them back to good litter habits without you doing much of anything.
With that said, you also have the added stressor of having multiple buns. Not only are they marking because of hormones (single rabbits do this), but they are also marking AGAINST other hormonal bunnies. Kind of a “double whammy”.
When are they getting neutered? I think you said in another thread that they have their surgeries scheduled, but I don’t recall when.
Litter-trained rabbits pee in the box 100%, and leave a large percentage of their poops in the box (90% maybe). You will likely always have some poop left outside. It’s similar to writing on the bathroom stall “Annabel was here!” (not that YOU do that, but you get the idea…) :o)
Beds (and couches) are hotspots for bunnies because they smell the most like US. Best suggestion for that is to completely block them from the bed. You may need to get an xpen for that purpose, or build some type of pen/fencing that you can place around your bed when you can’t directly supervise.