First grow, calcium deficiency?

It's because of the ph issue you had, she's struggling to uptake all nutrients, looks like nitrogen in your case.

A bit of sulphur and phosphorus might be useful too, but it's difficult to say.

The vinegar, after a few days with crushed calcium would break that down into like fine powdery stuff, yes. Though, you have to be careful with when you use that, too quickly and it'd be VERY acidic/varying (like high alkaline vs high acid spots, the egg shells vs the medium).

I'm having the same issue, I think it's because the fish mix has too much nitrogen for flower, they say to switch to the bio grow for flowering. I'd try that if you can get some. I'd stop the fish mix definitely though. Good luck.

Some more meta; -I do feed with biobizz fishmix, bloom & topmax. (I don’t know if either of them contains calcium). -living soil (I didn’t really bother with ph because i was under the impression that biobizz is organic and its living soil, the soil should balance itself out) -1 week ago the plant started preflower stretch like crazy, i upped the bloom nutrients 2ml/l & topmax 1ml/l & reduced the fishmix to 0.5ml/ml. Shortly after i started to see yellowing tips, so i thought i did nuteburn her. I checked the ph with a 3in1 cheap solar/water/ph thing and it was a little above 7, 7,5. I skipped nutes for a week after the yellowing tips & gave just tapwater ph’d down to 6 with natural vinegar. Then 3ish dats ago i noticed the brown spots on the leaves. I thought maybe it was lockout because the ph was relatively high, but then after researching ph absorptionchart of nutes, calcium does still take up at that ph. I did order a bottle of biobizz callmag but it can take 1 week to deliver where i live. I crushed 2 eggshells into a powder and added 1 tbspoon of natural vinegar, waited till the reaction was over and added it to water to feed the plant. The vinegar reaction should in theory free the calcium much faster than just letting it compost, at least that is what i’ve read. Some more experienced grower please give me some insight in the issue i’m having. Thank u!