Leaves tips turning purple during flowering (autoflower)

@Dedo_Verde_92 hi mate I do believe the plant/s are searching for nutrients mainly npk which is your nitrogen phosphorus and potassium I can't see anywhere where it says what type of feeding you are using so if its organic I would look at adding some fish emulsion or kelp some guano for phosphorus and for a natural carb hit plus sweetener and root microbe feeder add some blackstrap molasses OR if you use bottled nutes then a good dose of that over a week should help them recover some color Pushing them too hard with limited food will only decrease the yields and stress the plant so feed them plants Mate and good luck