straight undiluted into your rez? Tell me your not going this dude lol. That's a superb way to shock the fuck out of your plants in the buckets closest to the epi or wherever your putting the solution into.
I'm also confused as you first said your plants were eating 100+ ppm a day. Now you've mentioned you hit 950... Is that you adding in too much or the ppms now rising on their own? I'm running DIY systems, not the current culture. Same shit, different price. Few questions...
Do you use their top-off reservoir? or are you solely measuring your fluid level from your epi bucket? (How do you know how much they are drinking)?
What is your process of adding back / topping up?
When was the last time you did do a complete system flush? (As in drain the system, and put new nutrients and water in, not running straight water)
How much of the coco cal are you putting in?
When was the last time you calibrated your meter?
With UC, the best part is that if you start to experience something fucked up, you drain your system, mix new nutes, ph correct to 5.5, and wait 24 hours.
To me something doesn't add up that you've had zero pH fluctuations in an entire week. Thats a red flag. Especially given your ppm numbers have had a huge fluctuation on Sunday. Short of you monocropping the exact same cut and knowing what it needs at every week, you should have seen a fluctuation. Especially if your ppm hit a higher number for whatever reason. Id seriously take a look at your ph meter for starters.
I had a few issues with a calcium deficiency when I first started in these systems. The pH range is 5.5 - 6.3 as you know. Well I'd set it at 5.5 and then 2 days later I'd be at 6.0, and then it would seem to take forever to hit 6.3... I thought I had to wait to hit 6.3. In reality what was happening is that the plants were eating like mofos (water dropping, pH rising) and they are cal mag hogs in these systems especially with RO. Anyways, calcium is locked out above 5.8 or 5.9 so I was in essence doing great for the first 2 days, then locking my plants out for the other 3 or 4. I'd flush, pH adjust to 5.5 and then they'd do good for a few days until I hit the same wall again. If your pH meter is fine, and the stars alignment for that perfect balance in order for you to not see a pH fluctuation (which i highly doubt is the case), then you could simply drop your ppm's by 100 or 150. That would allow your plants to eat more than what is in the solution and then you would see your pH start to rise, water level drop, and know full well that your doing perfect. I don't believe in pushing the ppms high enough so that you hit that "perfect" spot and the pH doesn't move. Fuck that, that's a recipe for disaster and something will get locked out.
You need to get your system dialed in dude, your almost there. Stop worrying that your light is too close. If you think that's the case then put it up 6" - 12" and watch. I cant almost guarantee it wont affect anything.