There's a table floating around on this board somewhere that shows which nutes are absorbed at what pH. (It's different.)

You WANT some drift. High 6's is a bit out of the sweet spot but in my experience, no big deal unless you leave it there.

I had some pH swings in a coco test I did until I added the plants into the experiment. Then everything leveled out.

But if you can knock the pH down to a number you like, and it slowly and predictably swings back up through all the nutrient uptake ranges, that's just about ideal, IMO.