Well I guess that's the problem.
After pouring 13 gallons of RO water through (PH 6.2) runoff was still coming out at PH 7.5 !!!!!!!!! How much freakin water should be needed get that down below 7 ? The pot is only 3.5 gallons.
Anyway, gave up when runoff was just over 7 and then added more RO water with light nutes which gave final runoff exactly at 7. This will just have to do for now.

Should it be flushed again at next watering to try to get runoff to 6.8 or should it be good now until start flower? (which is at least a month out)