Are you using the armor si and calmag I see in the pic? The silica is going to raise the pH of your water to above 8 and add a lot of potassium so make sure you use pH down.
As for the calmag, are you using RO water?Your build-a-soil is already loaded with stuff and it looks like the beginning of Mg issue. Mg, Ca and K all need to be balanced for them to be effective. You could be unknowingly tipping the scale and causing an antagonism.
The last thing on my checklist would be temp/humidity. Make sure the root zone is not too cold or wet, and the air should be 72-80°/50-60% rh with good circulation. All the leaves should flutter a little bit in the breeze.
Plants can't move water themselves so they depend on "suction" from the atmosphere, and osmotic pressure pushing from the roots. If your soil gets salty, the pushing slows down (and can reverse and suck the life out of your plants) and if the atmosphere is too wet or dry the suction stops. When either of these happen the plants will move mobile nutrients from older leaves because it's not being brought up from the roots.
More info about exactly what you're doing and we will get you back on track.