Yes man... let them use up the nitrogen stored in the leaves and fade, they'll leave behind some purple anthocyanins sometimez. Nice work
you are almost there i would use plain water and some airflow maybe lower the lights a bit too! and let the pots dry out before watering again
I haven't given her any nitrogen though. Other than in veg, the bloom nutes were very mild. Only a slight burn on some of the leaves but tbh I don't think it was from nutes
what are you night temps ? Purple usually from cold chill . I am not concerned . I have done grows in the 50f