Lower leaves drying up upper growth yellowing

Iron defiency if I had to guess . Swap your calmag for some calmag+ that contains some iron.

I can tell you why your plant is unhappy - having a zip lock bag over her! Cannabis is not a rainforest plant. It does not need high humidity to thrive. Most native cannabis strain evolved in temperate, dry, low rainfall countries like Afghanistan and Pakistan. Even cannabis from South East Asia is usually found in low rainfall areas with a mild climate, with cultivation occurring during the "dry season". Those lower leaves have died and crumbled from being suffocated and from being kept in sweat lodge conditions. The yellowing upper leaves are probably in the first stages of being cooked while in the bag with the lights going. Please stop torturing your plant by suffocating it and cooking it, by placing her in a bag. Not sure I can give you any advice about DWC, but I think your Ph is too acidic. Please leave your plant uncovered and growth should return to normal and as long as your plant has decent genetics, all should be well. Hope this helps.... a grumpy old Organoman.