Does growth slow a little during the transition into flower

You are incorrect, the stretch is over now and growth is only in the flowers pistils. Keep feeding, she's reached her maximum height and she looks healthy🌱👍

Browsed your diary and depending on the Leds you use, the distance is very small. Then the water quantity cannot be right , so no conclusion there. And you should deffinetly crank up the feed. At this age they are hungry. Try a half/half Veg/Flower nutes for 2 weeks (at least twice a week) then Flower nutes for the remaining preflush period. Hope this helps.

I would lean on a unstable ph in soil test run off regularly

Make sure you are feeding at the correct PH and not over watering, looking at the leaves it looks like they have been struggling from nitrogen issues or a PH flux. I recommend just feeding PH water and letting the pot dry out for a few days to make sure you are not flooding the roots If your pots don't have good drainage