I've had this problem a number of times and it's a pain in the fuckin arse mate. Find out if your water is hard or soft. Hard is full of calcium and reads 7+ ph, soft is devoid of any minerals. Your water company will tell you depending on what country you live in, quick google.
Mine is hard, so when I added magne-cal it was causing the same issue you're having. Not sure about all that feed, can't remember what's been said already but you won't need grow nute now. Soil naturally ph's water and nutes usually get ph to 6.5 in my experience. I ph my water now, usually by the time I've added nutes it goes to 6.3-6.8. However, when I add molasses it drops a bollock and goes down to 4.6 ish.
So, check the water, if it's hard then flush the plant and give it a light feed in the last 2 ltrs, just root stim type stuff and flower feed at about 3 ml/ ltr. If it's soft it'll probably need cal. You're probably gonna notice it go south real quick regards the amount of black/brown spots but don't panic too much. Just check that water fella, it's the root of the problem one way or another IMO