My SLHs never make it to 10 weeks...9 tops...the start to yellow really really early...regardless of feed or pH...around week 5 the bottom most and larger fan leaves start to yellow out, no limpness, nothing sick looking...just yellowed...I just leave it be, and by harvest I have some awesome smoke...As far as I can tell it is just a leaf dropper...Leave yellowing starts a little later when I use Roots Organic soil vs. when I use FFOF but both give great results, but my SLH just yellows early too...perhaps I should worry or try to fix it, but I don't...and I won't...seems to be natural for the plant...I get a good yield, so no worries.