I have noted over the years, that high feed levels will first present as K deficiency, before there is a little spotting. Perhaps never getting to over feed signs, or they mingle with the K signs too easily. With 900ppfd you need high feed though, it's actually over some maximum recommendations.
My notes might be useless to you, with such different feeds. It would be interesting to see the run-off EC though.
It might be excess sodium at the core of it all. It pushes out K then Ca then Mg. Adding cal-mag like stuff may increase N, pushing the K out further. While lowering it's share of the anions. I'm guessing that would be quite noticeable, following the Ca-Mg addition. I think I have seen it myself, as we are perhaps fighting the same battle. My impatience is my biggest opponent though. I'm flushing them down to a root EC of 20 right now, basic feed, to see a few days of the problem developing without me putting so much extra in, that it's no different to just increasing my basic feed.
Leds at 50,000 lux (~800ppfd) is hard work. You are doing better than me if I'm honest. I browned a few hairs at 4 weeks. Undeniably over fed, and likely to taste off to my palette. I don't know what I was thinking..
I don't believe it is excess nutrients pushing out the K, Ca, Mg. But I have been wrong before. And I do believe I am feeding to heavy.
And the Cal/Mag nutrient I added has not nitrogen in it and is why I used that one. I only plan on giving it one shot of cal/mag. I am already at day 45 out of 70. Really just 68 for this strain. Since I will be flushing for a week that only gives me another 18 days to feed them. But I will have to see what happens to say for sure 100%.
I know this feed mix is not perfect but will get me across the finish line.
So When I went into the grow I took a few better pictures for DHF and others of the calcium deficiency. These are better pictures and show the problem better. I was just trying to show it was on the newest growth on the bud. But it didn't show up as well as it did on some of the slightly older leaves. These picture are still new leaves since they went into flower but are still like about 30-35 days old leaves.
I know how hard it is to tell the problems with a plant with just a few leaves. Especially when using a camera that does not show the colors as well as standing next to the plant. I have the benefit of looking at hundreds of leave very quickly. So don't think I don't appreciate the comments. I understand you can not see what I do all the time. And I am always learning stuff from posters here.
So thanks guys for the comments.