That's magnesium. See how the veins of the leaves remain green?. Get dolomite or garden lime (2tbs per gallon) this will help with your soil that's probly getting too acidic, get some Calmag plus to folliar feed so you give her more trace elements she's needing while the medium stabilizes, a "Micro" type of fertilizer would also work, rememeber to use very diluted concentrations when folliar feeding.
When flushing with Dolimite make sure the PH reads over 6.5