As someone who owns a litter runt, be wary that general development and immune system may be a bit compromised. While Wick is remarkably quick at recovering from surgeries, items that require immune system response, like upper respiratory infections (sniffles) and ringworm, seem to take him very long to get over. Also his small stature has led him to have crooked teeth/jaw, so he gets that addressed every 5 weeks at the vet.
Not all runts are the same, but just keep in mind smaller size may have it’s consequences to health!
Saw dust isn’t a good option at all, so that switch is definitely good. There are many litters advertised for rabbits but are actually quite bad for them.
The sooner the better, but if she isn’t losing hair rapidly, scratching herself aggressively and just generally harmong herself, I think waiting a couple days if needed won’t be life or death.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.