Magnesium or nitrogen ?

[castle]

The ph pen I was using capped out...so I'm using drop test.

The feed was 6.5, runoff was closer to 5.

 

[Muddy]

I don't trust the accuracy of those drops but it does indicate your soil pH is very low. You will need to add some dolomite, or garden lime, to your pots. Add 1 tablespoon per gallon of soil, mix it into the top layer and water it in. Don't expect to see immediate results. Lime takes about 2 weeks to become activated and effect the pH. In the mean time you can do foliar feeds to get some nutrients to them. If you haven't seen this already, here is a chart that shows the pH levels of where different nutrients are available to the plant. You can see that at such low pH, all the primary nutrients are locked out and unavailable to the plant.