ive kept some hornworms that grew too big to feed my leo because I thought it would be fun to raise them. they have all made it to the pre-pupa stage, but Ive had three die rather than doing the final shed to become the pupa. didnt have luck with using soil as substrate so I used shredded paper towels and tissues which they burrowed under. does anyone have advice as to why mine are dying? temp is between 70-75, moisture is low to average. no mold or excess poop or old food.