Senescence (the condition or process of deterioration with age) is normal with plants mid-late flower. I've grown ILGM's white widow auto twice also and what I've noticed is two primary phenos, a short bushy one and a taller one - you have one of each. My observations with them were that the taller pheno always faded out first - not sure on the mechanism behind it but your shorter plant is starting to lighten a bit and will probably start fading soon too.