What problem? The leaves in the center look great. The darker veining showing in the leaves is because the plants are taking up the fertilizer. I am sure due to the Neptune. I use it all the time myself. Great Stuff. Never tried the Chickity Doo Doo.

Maybe some powdery mildew starting on the bottom leaves? I can't tell.

Maybe this is a better picture of the problem.
White on older leaves is actually Surround (Kaolin) - was trying against cucumber beetles and for some sun protection during the heat wave

Pale leaves with darker veins. Was lacking nutrition and now taking it up.