Wow Lit Up, thanks for taking the time to go through all of that! That is an interesting analysis of the situation. One that I haven't thought of. However, I didn't actually remove the plants from their pots and trim the roots. I cut about 4 inches off the pot and "loosened the roots", then I stacked it onto the new pot. The root structure should have remained intact. The soil at the bottom wasn't exactly dry, just drier than I expected.

I have been trying to figure out if the plants have been suffering from under nuting or nute burn. To my untrained eye the two conditions seem very similar. The low pH, combined with the small amount of nutrients used, makes me rule out nute burn. I just can't figure out why the pH drops so quickly after flushing. Another thing, the plant on the right is a castrated hermaphrodite . It has been treated the same as the other two. It's not showing the same symptoms. Hmm.

I believe that you are right that the roots are the problem area. I'm hoping that this isn't the signs of root rot. I seem to be caught between a rock and a hard spot. Live with the low pH, or correct it by overwatering. I hope I can fix this and let the plants mature. At the very least I want to find out what is causing the problems. Sounds like a job for Sherlock Holmes imp: