My medium is a perlite vermiculite mix in hempy buckets. When I water my plants with ph 5.7 water the runoff will be in the ph 6 range. I think that what water is left in the reservoir at the bottom of the bucket from the previous watering is to blame for. Because I dont think my medium would change the PH. So should I water with say ph 5 to compensate? Or is the PH of my runoff misleading me somehow? My thought is that if the PH of the runoff is so high then I should water with low PH and they will cancel out. Its been like this for most of the grow and I've been trying to keep the ph down with flushing and watering with a lower PH but It always raises a bunch within the first day of watering. I'm going to flower them soon and I want to make sure the PH is on point so let me know what you think the runoff PH should be and how I can keep it there.
In soiless media, I like a runoff of ~5.8-6.1 depending on the stage, but different strains do react differently. Better calcium absorption at ~6.1. Its nice when the solution drifts up like yours. Best of both worlds. Are your plants healthy? I wouldn't change a thing. The absorption of nutrients by the root system affects the media's ph.
I've been trying to get the ph and nutrients tuned in but it seems if one is on the other is off. I've had a few problems here and there throughout the grow. Deficincys from not feeding enough and to off of a ph. Ive also burned them a few times. They seem really sensitive to ppm change. Just recently the new growth got real yellow. Im pretty sure it was a deficiency from the PH staying too high too long. So its really been touch and go this whole grow. It's my first time with a soilless medium and I'm still learning.
To me looks a bit like a mag def. Reviewed your messages. Are you using tap water? What is your water's EC before adding nutrients? You don't describe what you are feeding and only tell us pH, so its not always easy diagnosing.
I'm using the General Hydroponics Flora trio nutrients with calimag. I'm mixing up some nutrients right now and I used 13.8 ml of Micro, Grow, Calimag and 6.9ml of bloom. This is for 3.5 gallons with a PPM of about 710. That's including the 38ppm of my tap water. According to this chart and some research I did it looks like it was a Manganese deficiency. The symptoms matched and the PH of the runoff had consistently come out over PH 6 before it happened.