Having significantly lower runoff than input, as well as higher pH from run off seems like it’s hungry personally.
Something is almost immediately displacing that feed and spiking the pH.
So it could be the roots are hungry and quickly up taking the feed, or the coco could be stealing some of the feed if not properly buffered.
When the dissolved salts in the feed are immediately displaced, this causes the pH to go up because most nutrients are slightly acidic.
I know it’s weird you have slightly burnt tips but that’s my best guess is up the feed a bit, or double frequency of feeds..