I read a very informative article about overfeeding P and/or K, as well as everyone's favorite,
Cal-Mag. The interplay between too much Potassium and the resulting inability of the plants to take up Nitrogen was very interesting, since it fit the bill for a lot of growers who are seeing yellowing leaves after using a fairly strong blooming potion. There was also info about Manganese (I think) causing Calcium to be un-available and causing signs of deficiencies, while the problem is actually from overdosing on something else. The Ph range was surprisingly narrow, with levels lower than 6.0 causing problems. With everyone keeping their Ph pretty close to the 6.0 level, it isn't surprising that these problems pop up. Of course, alkaline soil is also problematic but seem to be less likely than an acidic medium... plus many nutes are acidic and can contribute to these issues. I couldn't find the URL for the article, but I found it researching NPK usage under various conditions. It's a LOT more complicated that I really thought, and actually makes diagnosing problems more difficult, since a simple N deficiency might actually be from too much P or K in the soil, compounded by Ph dependent reactions.
This doesn't really apply to your current step in this process, it was just an offshoot of considering yellowing leaves and dried/burnt leaf tips and it kind of went from there. One thing I did pick up was that it is best to go easy on nutrients unless you either really know what you are doing, or that you have the ability to determine Micro and Macro nutrients. I've come to the conclusion that it's almost impossible to correctly diagnose something without decent lab type equipment, since any particular symptom can have a half dozen possible causes in addition to the obvious ones.
OK... enough for random, stoned thoughts. It gets hard to keep focused enough to make whatever point I started off trying to make.:cool: