Grow Mediums DWC Cal mag issue in flower transition

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Good morning!

I have been growing for about 2 years now and have mostly been using coco. I decided to mess around with DWC in a couple of my tents and am having a consistent issue and can't seem to figure it out.

I am using Advanced Nutrients on one of the DWC and Megacrop on the other one. The grows make it through veg looking pretty amazing....then it happens. Each of my 6 DWC seem to be showing Cal Mag issues (brown spots on leaves) but ONLY during the transition from veg to flower. They seem to recover and flower out well but I want to understand why it's doing this and how to prevent it in the future.

I have bumped up cal mag during this transition. I have tried backing off of the dosage. I have tried leaving it out and bumping up the base nutes. No matter if it's AN or MC, I end up with this issue.

Any help would be appreciated :)

Thanks!
 
My guess is pH is dropping too low during transition and locking out Ca and Mg.

hydroponics-ph-chart-marijuana.jpg
 
I guess I will have to monitor it like a hawk this time. I spot check every evening and keep it around 5.8. Thanks!

I keep pH closer to 6.0, maybe pH is too low?
Too much light?

I don't have these early problems in DWC while keeping EC below 1.0
Mine happen during mid-late flower when too much food and/or light can be harmful.
I've got a plant (mephisto DeepBlueC x SourBubbly) at 8.5 weeks with burned tips from EC=1.0, and have had to go down to EC=0.8 - 0.9
But I use the high humidity the VPD chart recommends, which might affect things.
 
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