low RH. the plant will use more water, but the nutes in the water will become concentrated in the leaves, like salt building up on your skin when you sweat, except it's inside the leaves, they don't sweat like people, they transpire, which is similar, but different.
this will slowly cook them from the inside out.
lower the temp slightly, and raise the RH at least a couple of points. also drop the ppm of your nutes a little, till you get the other problems dealt with