Okay, so trying to trouble shoot this comparison is getting a bit scattered. I'm doing my level best to make the Vulx plant a clear winner as I believe they're claims must have merit, but figuring out the reason it's lagging behind the regular plant is not easy.
We've covered pH, chloramine, overwatering, too frequent watering, and not enough product added to the ProMix. That last point is something I raised with their rep when I mentioned that 5% of the weight of the ProMix might have been insufficient given how fluffy ProMix HP is. Most of the folks using this are in soil I believe, which is a whole lot heavier.
I was going to up-pot to 5 gallons and change the ratio of ProMix to Vulx based on a new calculation, but I was stopped and told that, based on what they were seeing, I was giving it too much water at one time.
This seems patently absurd to me, as the roots need to be wet from top to bottom, but since this is their product I'm testing, I am following their recommendations having registered my objection.
By yesterday, the ProMix was so dry it had shrunk away from the edge of the pot. As anyone can see from last week's pic, I let my soil get dry before I water. There are no "wet feet" or nutrient deficiencies
from overwatering:
Here were the roots yesterday:
I gave the non-Vulx plant 32 ounces of 4.5g/gallon MC, but gave the Vulx plant only 16 ounces of 2.25g/gallon water. Knowing that would leave the the bottom half of the soil dry as dust, I split the water in two parts and bottom fed 8 ounces and top fed 8 ounces. Here is the obvious result, with a bone dry gap in the middle:
It looked the same this morning.
I have no idea why they think the plant is being overwatered, because the leaves show it starving for nutrients. I think it is much more likely to need more product over less water, but I will follow their instructions.
More updates as they occur.