PH was exactly the same this morning as it was last night, so it looks like the buffering was what I needed.

Ok, today I did a nearly full res change. I left about 2 gallons in there. I used a slightly weak lucas bloom formula with about 8 gallons of RO water. (I used a formula for 7 gallons when I have a 10 gallon system). Poor plants have been through alot, so I'll see how they behave.

After it had circulated awhile and I adjusted the water level, I ph up'd using a few ml's of the baking soda and water. It took very little, and I'm currently sitting at 5.7PH, 650PPM.