so i have 3 strains going in my flowering room in 5 gallon pots in Coco Coir. I have plenty of light on the plants. I have been using Earth Juice Nutes since a week before they started flowering, and they have been flowering for 3 weeks now. I use the five part serious, Grow,Bloom,Micro Blast, Metta K,and the Catalyst. I have been going off of the back of the bottle and it says to use all five every feeding so i started them off on 1/4 srength and have moved them up slowly to almost full strength. I also use THe big bud powder now that i am in flowering as well as Cal Mag from botanicare for the coco(has to have it with nutes) about a week ago a few of the plants started to turn yellow. Like the whole plant is still healthy the leaves are just turning yellow but some of the other plants are still all green. It is also green where the buds are forming just the fan leaves are yellow. Temps are about 85 when lights are on. I cant get it any cooler. what would cause these leaves to turn yellow all at once .Thanks.

By the Way i just watered them with fresh water a friend told me to give em a fresh watering one time. Ph is also always adjusted after the nutes to 6.0.
I will try to post pics tomorrrow

they also have purplish stems on the ones that are yellowing

This is normal. When a plant buds it is nearing the end of its life. As it matures, it drops leaves. If you dont want the shade leaves to drop, you can foliar feed the specific leaves with some vegetative ferts one day then water the next and they will green up some.

Are you using a complete fertilizer, AKA one with full trace elements?

We love pictures here.

The grow sounds like it is going according to plan,during the flowering phase the plants draw all the goodness out off the leaves and because the plant is no longer produceing vegative matter ,it''s in the budding side of the grow all the feed that went into feeding the whole plant 90% of it is going in to makeing them buds fat.this sounds fine i would give the plant a flush though they may be excess salt build up,just flush the plant with a ph of around 5.0/5.5 then leave to dry then back with your normal regiment of feed and shit that is alot of feed.

5.0 for soil flush?

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its in coco coir