Is it normal that my pump after power pump is less than usual? eg.. Usual 1 pump is 30-40ml 6am power pump 9am pump will be 20ml..

I agree the yield varies for each session and for me there's no definite trend or pattern, can be different everyday, only overall daily output about the same. With power pump you should gradually see some improvement.

Yield does depend on so many factors. Diet, water intake etc. But yes, it’s normal after a power pump. I kept it up, and eventually pumping output increased.

The supply also varies within the day. Maybe that's why you pump more at 6am compared to 9am.