It's pretty much all speculation at this point. The labs, albino labs in particular, have been known to have weaker immune systems. In my opinion, this problem is the direct result of too much inbreeding to produce the morph. Inbreeding of reptiles has the same affect it has on mammals, it just takes a few extra generations for the problems to arise. If you take a lab, then breed it to an albino to produce double hets, then breed the double hets back to the lab parent to produce labs 50% possible het albino, then breed the labs 50% het albino to each other to produce albino labs and various hets, and then breed the albino lab back to one of the proven het albino labs, you can see that is a ton of inbreeding. When this is done as quickly as possible, without regard for the integrity of the bloodline, it causes problems.
This is part of the reason I have chosen to keep a normal female around. So that I can breed morphs to her and produce hets that have new blood in them.