Were you able to flush? One issue I had on my last grow was a P deficiency. As opposed to changing the mix, mine was a result of the pH being too high for soilless mix. Where I used to run around 6.0, I started taking it to 5.7 (and even a little lower) on both my water and nutrients, which ended up fixing the problem. Since you're growing in real dirt, you pH would likely be a bit higher, but something you may want to consider.

Farmer Rich