Yellow appearing on some leaves?

an 85w light is unlikley providing 750ppfd unless it's barely 2 sq ft, maybe a fraction more... and only if high efficacy diodes driven at proper wattage to achive said high efficacy. yellowing from bottom-up and tip in will be a nitrogen related. think you have something more complicated than that to fix. seems like you've picked the amount to water vs the reality of the pot size and plant size dictating how much water is given.. irrigation habits could definitely be part of what you are seeing. some sort of buildup and deficiency at the same time. FF nutes are lacking in several ways. it's not a complete diet and it isn't in proper ratio. find others that have figured out how to ride that needlessly complicated bike. mimic what they do.. best you can do with FF ferts. stop choosing how much water to give.. that's hubris. you water until the whole thing is wet. with soil you want limited runoff excepts when trying to fix an imbalance or a toxicity etc. soemtiems it's just worked into irrigation cycle, but if you regularly have to flush the substrate, that just means you are throwing out significant portions of fertilizer given previously.

Hi Good fellow. What soil you using for? Maybe soil already gives enough nut and nutrients mix is not necessary. Water with ph balanced clear water, check run off water ph level.

Maybe nutrients toxicity?