With using the app on my phone and comparing it to what the manufacturer has said the ppf should be at what distance it is very very close. I moved the light high as it could go yesterday haven't been home sense today I will go over the vpd scale you gave me
Good to hear! That's a great way to get things dialed in.
Now that the issue has been diagnosed as a nutrient issue, how about giving your plants more food?
Re. "very very close" - is "good enough". The goal is to get the grower in the ballpark and then they can adjust as needed. An Apogee is calibrated to 5%±. A light meter+conversion factor (which is how Photone works) may be a more inaccurate because there's 5%±, in the case of the Uni-T, as well as, perhaps, the conversion factor being off. But that's fine because even if it's, say, 10% off, that's only 100µmol at high light levels.
I usually take light readings daily and, with the plant at it's current size of about 2' x 2' x8", I take nine samples.
These data are from yesterday. It's a Growcraft X3 at 292 watts. The plant is in day 44 and the schedule is 24/0. The canopy looks level but, looking at the numbers, it looks like the light is crooked and/or the canopy is lower in the back left and rises to front. And there's a difference of 150µmol± between those two spots.
It's like raising kids - just give them the best conditions you can and watch them grow.
Now that I think about it a bit, we
do vivisect them and then burn them so perhaps the "kids" analogy isn't quite right…