Leaf issues with pictures. My most problematic grow.

classic calcium deficiency. seems like a few people have mentioned to increase your inputs for this. Good luck with the next grow! Hope it goes perfectly!

I am not an expert so I typically follow the instructions on the bag or bottle. I use tap water pumped from the lake and it starts at 0.1 EC. I add a little Cal mag to at least make sure I’m not deficient and then mix up my nutrients. If my EC is too high I add more water. I then check my PH. If it’s within reason I leave it alone. More than 3 points off and I correct for it.
I’m not comfortable adding stuff that is outside of the manufacturers intended formulation because if something goes wrong it starts a cycle of guessing.
I’m a strong believer that if it works don’t mess with it.

Manufacturers recommendation for what exactly?

Tomatoes, zucchini, hydrangea or any other non cannabis related plant species. Add to that if you're growing in hydro you're using about twice as much as you need.

What works isn't always what's best.

Personal opinion!