Do you have the actual temps and humidity? If you're struggling that much with humidity, I'd switch to cypress mulch or coco fiber to bump it up. You can also make a humid hide by adding some damp (not wet) spagnum moss under a hide, that way they can self regulate.

I don't think there's anything wrong with darla's shedding schedules. Babies shed pretty darn often. That said, each snake grows at a different rate and as such will not shed on any set schedule.

Quick question, are they housed together? And what's the setup like?