brown spots

The ph might be too low, and locked out and won't uptake nutrients properly. Flush with Ro water if possible at 6.5 - 7 ph and see how it goes. Avoid to feed every time you water especially with 900 ppm unless you have a massive plant. Good luck!

u got late nitrogen deficiency along with calcium and magnesium. Do not flip to 12/12, fix it first. U can try raise Nitrogen by 30%. And spray all the leaves with nitrogen and calmag nutes just after light go off. Cheers

No diary, terrible pictures......hard to offer help other than I wouldn;t go to flower until they recover healthy growing........looking very pale green, but that cold be down to the bad lighting. Always post pictures taken under "normal" light, not grow lights, and close up pictures too.

Water less. Your plants looks over watered and frankly they could be experiencing root rot. I would let your soil dry out before you water. When pot feels light, then water, if it's heavy, don't water. If you start doing that and your plants don't bounce back then you got root rot goin on and you better act fast with an enzyme to address it or your plants will die.