Could also be a case of TOO much potassium/magnesium, and the levels have become toxic to the plant. I would take one pot/vine and add nutrients, keep one pot/vine the control (keep it the same), and take one pot/vine and use regular ol' basic soil. That would give you a definite answer to the problem, and important information for future growing.
Good luck! Out of curiosity, what hop strand are you growing?
The hops are centennial.
I have used a mixture of mostly mulch and local soil (in Hawaii).
I have been having much difficulty with the soil and keeping the white flies off the plants. The white flies are so bad, I am using neem oil to keep them off and they still are killing my cascade!
Look at the bottom of the leaves, look for spider mites, they may look like black pepper type coating on the leaves, you can take a piece of white paper and hold it under the leaf, tap on the leaf to see if a ground pepper like substance falls onto the paper, if so, those are spider mites.