Blueish leaf tint?

Don't just throw more Cal/ Mag at it until you confirm your pH is correct. If it's off, the plant can't up take it.

if your soil PH is off and the water is a low buffer, that wont fix the PH of the soil. You should check the runoff and PH the water accordingly, flushing the soil with ph corrected water until the runoff PH is right.

I'm using RO water. I've seen magnesium deficiencies. They need calmag.

RO water has very little buffer - it's about as low as it gets. The soil runoff (the one time I checked) was at 6.4. I'm going to stick with watering at ph 6.6.

RO water does not guarentee your PH is right. It just makes it much easier to keep it right.... Instead of using a quarter teaspoon of ph down u will use 1 drop. some nutrients knock the PH out of wack, and as the plant pull up certain nutrients and leaves others behind the soil PH will change.
You need to check ur runoff and read it.