Here's an update.

- Added larger fan (swamp cooler) to blow across the top of the plants to reduce the direct heat from the lamp. Now it generally doesn't get over 90 degrees in there and RH is still never over 40%.
- Did a heavy watering with plain ph adjusted RO water.
- Decided not to do anything drastic and just see what happened. Ready to sacrifice if necessary.

Took a few days but what do you know, all of a sudden everything just kicked into high gear. They have grown more in the last few days than in the previous month and signs of nute def's are going away. They are all looking strong.

Thanks for all the tips!