To make a long story short - I was lax in testing my RO/DI and didn't change out canisters for a long time. Found out when my tank water went haywire that the RO/DI wasn't filtering too much of anything and putting basically tap water in my tank!
I used my normal test kits (ammonia, pH, nitrate/nitrite, phosphate, salinity, etc.) and found this all out - - water coming from your RO unit should be neutral to acid in pH, no other stuff in it like phosphates.
I changed out the canisters and now have great water again. Lesson learned! I will be sure to change them out regularly from now on, especially the carbon block and micron filters (every six months max).