What is this

Lacking in Magnesium, this is quite common if you're not regularly checking the pH of the water and the soil. Too f far out of the required range, and it's ability to uptake certain nutrients difficult

Ca,Mg,P lock due to K excess

Magnesium deficiency.

Looks like you might be dealing with a magnesium deficiency or early pH imbalance The dark areas between veins and the light green edges are classic signs. Check your pH first if it’s off, nutrients can’t be absorbed properly. If pH is fine, try adding a small dose of CalMag and see if the new growth comes out clean. You caught it early, so she’ll bounce back fast