could it not be healing because they drink out of a bowl?No, you probably don't need to worry about flystrike, but I don't think that gnats are the cause of the scab and other issues. Something else is still going on and I think you still definitely need to see a vet, especially because this a recurring problem the bunnies have had.
we are getting them to the vet as soon as possibleWhile the scab getting wet may not be helping, it certainly isn't the root of the problem. Just hang in there and get them to a responsible, rabbit-savvy vet as soon as you safely can. If this has been a chronic problem it's unlikely that a few days will make things too much worse, however, continued home remedies and improvising won't be what solves the root cause. Take this from someone who seems to need to improvise a lot, it only works if you genuinely know what you're doing, and in this case, I think professional help is needed.