Right on brother and here is where you on one up on me with numbers. I don't have a PPM meter And just try to watch my plants to look for anything wrong. If your ppm numbers have been 1300-1400 to the recommended 300-500 ppm is not slight in my eyes. I think we are both now better understanding the side affects of overfeeding with these nutes. So both
rmoltis, and
justiceman bring up a great point about nute lock from overfeeding.
Here is an example of an acidic nute lock that happened to me a couple of years back with a PH crash from 6.2 down 4.6. The reason I want to show you this because of your yellowing problem is with no leaf burn.
A few days later and toast!