Calcium during mid to late flowering?

[felis]

In week 4 / 5 of flowering, I got what appeared [ to me ] to be a calcium deficiency......a few leaves with "rust" blotches on them.
I've been adding 3 ml of calimagic per gallon consistently, right from the early veg stage to now. Yes, it may seem like alot.....but my tap water has low ec. Better to be safe than sorry right?

I've kept the ph from 5.7 to 6.2 allowing for some drift, but "mostly" aim for 5.8 to 6.0 I even kept the ph at 6.2 for two days hoping that enough calcium would be taken up.

Night temps are not too cool.......16 or 17 deg C

RH is around 40 to 50 for the most part of flowering.

So, I added a little more cal mag to the nute mix to ensure that the coco is being fed appropriately. Yes, the Canna coco was buffered by me as well.

At this stage of flowering with no new leaf growth........how do I know that the calcium deficiency has been corrected? No, those damaged leaves do not resolve even with treatment.........we all know this.

Thots please?

 

[TysonOG]

2 thoughts, both when I got what I thought was Calcium deficiency at that stage of flower.
Once it turned out to be salt buildup in the medium (this is when I was using coco)
Now that I'm in hydro, I had a plant that looked like calcium def around week 4 of flower. Turns out it was the beginning of thrips. (you can tell by the shiny, silvery residue on the top of the leaf)

The main point is, at this stage of the plant, it is rarely directly calcium def. It is nornally brought on by something else.