Check the temps. Make sure they're 91-97F on one side and 80-85F on the other. Three hides, I'm sure you know the break down, etc.
Runny poo can be caused from a parasite, only a urate (white part) can be caused from impaction, stress, change of diet.
I have 3 leos who spent 48hrs in a shipping box (they got lost in the mail unfortunately),and still have runny poo from the stress. They've been checked by the vet, and it's just stress.
My adivice, take a fresh poo off the paper towel by cutting a square, put it in a zip lock, and put it in the fridge. Do this every day for two or three days. If they don't look more solid than the day before, take all the samples with you when you take him to the vet. If it does not improve at all in about 3 days take him to the vet. He could be sick. With the samples in hand, it'll make the job much easier for the vet. Make sure you take detailed notes of his behaviors and behavioral changes taking place. Write down how much he's eating exactly, what you're dusting, and the temps recorded every day along with the air temp in the room. Get as much information as possible to show the vet.