Are the yellowing leaves soft and supple or hard and crispy? Normal yellowing is soft as the plant starts drawing mobile nutes from it's oldest leaves first. Hard and crispy is toxic salts buildup and you don't want that.
Genetics plays a big roll in the colouring of plants as they near their end. Think maple trees in the fall. These are the most colourful plants I've ever grown. OG#18 that I harvested last June. Glad I got a cutting to grow more as I find it's my go-to toke in the evenings when I want a pleasant but not overwhelming buzz for sitting in front of the idiot box.
View attachment 4059459