It sounds like you're WAY overdeveloping. According to the Massive Dev Chart, both films should be developed in XTOL 1+1 for around 9:15 to 9:30. No wonder your negs are anemic -- you're effectively pushing the film several stops by adding on extra time.
And the fabled XTOL sudden death syndrome is much over-hyped. It was a product of the discontinued 1L packets. I just finished off a batch of 5L that was over a year old and worked as well as the day it was first mixed.