in nature, where no one is over feeding them, plants will always look like yours by the time all the trichs are cloudy. they're forced to consume the nutrients in their lower leaves to feed reproductive growth. the plant also starts to produce ethylene gas, which causes ripening in fruit and vegetables, but it also causes leaves to fall, usually after the plant has absorbed most of the nutrients stored in the leaf.
the next plant you grow, feed it veg food till it stops stretching, then switch over to flower food. it still may do this slightly, but to a much lesser degree
and honestly, that looks like it may be genetic coloring, it doesn't seem to be eating itself too drastically. you may get lucky and get some purple buds
