A gradual increase in your PH from 5.8 to 6.2 is good as your plant need higher intake of different nutrients and mineral when flowering. I had found a chart which can from studies showing a different range of preferable PH level over the course of a cannabis plants life. If I find it I'll send it to you. I personally would not increase your feed over 1000ppms unless you are very comfortable increasing. Only you can know for sure how your plant is reacting to those levels but at any sign of tip burns you'll need to back off instantly.