Early Bloom stage started. Definitely, the feeding schedule I used did not have enough Phosphorus.
I switched to GH simple program
Day 49 pH is stable, no adjustments. Turned off air pump yesterday and forgot to turn it back until today. 24 hrs without functioning air pump. The plant looks healthy, roots look healthy and I wouldn't dare to get the plant out to wash the container. Roots look very heavy, and this mass needs good support.
Lessons learned - I have some time in case of power outage or pump failure, got new backup air pump