Coco runoff pH really low?

Are you supposed to test runoff pH in coco coir, and if so, what should it be? I've been watering with 5.8 pH 1/2 strength nutrient solution once a day. I tested the runoff a couple days ago and it came out at 4! I flushed it until it came out at 6, and now I've been watering with 7.0 pH solution with the runoff at 5.0. That still seems dangerously low to me.

Don't worry about run off ph. You will really hurt your plants watering at 7 ph.

Run off ppm is important, not ph.
run off ppm should be lower than what you are putting in

Got it, thanks. I'll go back to 5.8.