Cracking fur is typical in dry air conditions, though it is associated in health concerns due to poor nutrition. This usually will be accompanied by other symptoms, you may need to watch closely to catch as gliders hide illness. However, BML has been a successful diet used by many, so I would tend to conclude that in their case it's not diet/health related, but most likely dry air conditions, this has been the case for my gliders. Even though I did loose my Lulu, my other two have been fine and show no signs of distress or illness. My gliders have been on critter love diets, but had gone short-term on EN brand HPW.
I don't believe diet had anything with my Lulu's passing, she was an easily stressed glider from the beginning. She was an Over-groomer, which I had consulted vet about when first signs of baldness appeared, this was years prior to her passing, so I believed the reoccurrences were related to her just being easily stressed, as it's the case in some gliders (personality/disposition), I do feel though that the fact she was easily stressed contributed to her shortened life, as she appeared in her normal state prior and because of the condition I found her. She was about 6 yrs going on 7, being rehomes, I have no conclusive OOP dates for any of my gliders.