Alexaanswered grow question 5 years ago I had same problem i think. I aimed my PH to 6.5. The i feeded them by Cal-mag Sensi which contains Mg,Fe,Zn. I also added more PK for once.
Then i just added some enzymes and root boosters.
I really think your main problem is in Magnesium. But i would also add that Fe and Zn if its possible for you ✌️
I am not sure if its gonna help you. You can check my 2nd rqs grow where i had same ishue in previous week and i fixed it by these nutries.
I am curious what others will say to it.