What it can be?

In my opinion up that Cal mag Autos are needy when it comes to Cal Mag hope this helps

Gotcha. There’s usually other important elements/compounds aside from the N,P, & K in each bottle of the three part so keep that in mind

@Ezzjaybruh I've cut micro and grow due to fact all those nutes contain nitrogen micro 2-0-0 grow 1-0-4 bloom 1-3-4 so I think there is to much nitrogen to what actually plants need for flowering on top of it calmag xtra is 2-0-4, on top of it I had really dark leaves and clawing and I narrowed it to overfed on nitro cause watering and windburn wasn't possible

@GrowingGrannie @AsNoriu Ok cheers will do next few watering with higher pH water

If you're growing in soil, your pH is too low... the plant can't absorb calcium if the pH is under 6.0 (6.2 is ideal for ALL nutes the plant needs) so that's got to be raised... you can give it all the calmag in the world and if the pH isn't right, the plant can't get at it. Good luck!

So go with 6,5 for few, raise it to 6.7 one watering and let dry out,your run off is the answer - your soil/medium is wrong ph .

Why have you cut off everything but bloom ? Those are meant to work in conjunction with each other in a micro/grow/bloom set up. You should be using all three or at least micro bloom for most of flower

@AsNoriu Ph 5.8 is runoff the not the water I use for watering. Watering is with pH 6.2/3 And for 2L of water I use on that pot I get around 400/500ml runoff

Ph and all after it, correct it, add calmag only for few waterings or even foliage, it looks like you still have time( i normally stop spraying anything on week 3 of flower) Make sure good watering cycle wet/dry/wet/dry 5.8 is for coco, so i hope you have small run off too All should be fine, some leaves can still go worse for first week

Couldn't fit everything what I wanted to say in question, so here is continuation, like I said I never used nutes stronger then 50% of recommended dosage, definitely not a bug or insects cause can't see anything on leaves with magnifying glass