Totally inspired me to make my own! Thank you for being so thorough. I will be making one that is double the size and I will let y'all know how it turns out.
You have something for sure. Mites are really hard to see at .4 mm like 1/64 of an inch. Those yellow spots don't look like a deficiency. Use azatrol like 3 times in a week. Potassium is much larger spots. Azatrol would be a safer alternative and it is good to apply to healthy plants anyways.