Help with Thinning and Yellowing Leaves – Need Advice (14 day)

It's simple really. If you're chart is correct. You're feeding every day? With seedlings you feed once a wk. Myself I leave them for 2 weeks sometimes and just use Epsom salt as a foliar spray. Seedling roots needs air in the root zone. Yours are showing signs of smothering. Stop giving fluids and keep a higher RH. Less is more with growing. 1-2 small feeds a wk. Not every day. Or more than 1-2 300ppm npk grow feeds with enzymes or root stims in-between if you want. But, let the soil dry up.

if that is soilles, you need to be closer to 1.3-1.5 EC... local vpd will impact that. higher vpd = lower concentration needed, all other factors the same. overall concentration doesn't gaurantee each nutrient molecule in in proper ratio. That you dial in by observing and adjusting based on what the plant tells you. If done right a good formula should work on 95-99% of plants without seeing any symptoms or if you do so minor it doesn't matter. also, if in soilless, you don't pick a volume of water to give. you give enough to get 10% runoff waste water outthe bottom or you aren't doing it right. the runoff is integral to maintaining a consistent level of nutes around the roots. This makes diagnosing and adjusting the formula consistently effective. soil is more complicated due to unknown/variable nutrient contents of the soil. you also don't want to get 10% runoff as that just wastes the pre-amended nutrients, but you still give enough water to fully saturate the substrate. Wait for top layer to dry, then repeat. a good wet-dry cycle promotes deeper roots and reduces risk of pathogens. you can go be the weight of the pot for best trigger. how much it dries on top varies by substrate type. you seem to be over-complicating it. No need to wildly change your fertilizer formula unless reacting to the plant. if in soilles medium: 120-130 N 40-60 P 180 ish K 100+ Ca 75ish Mg 100+ S is a good starting point for vegetative phase and several weeks into flower. When vege growth abates, i lower N to ~100ppm. This is a low EC starting point. Your vpd differences from mine may need more or less. Easier to ass than take away as far as adjusting to what you see in the plant. the plant dictates everything not some preconceived notions.