I went back and re read this thread again and I going to put this out FYI.
The iron that you choose to add to the recipe depends on you PH.
Ferrous Gluconate and Iron Chelate 13% EDTA are good for acidic ph ranges.
Iron Chelate 11% DTPA is good for Alkaline ph range.
For the first time in several months my plants are making a tremendous come back. I actually had to pull leaves and excess growth out yesterday. Phosphates are coming down to a normal range again and I'm able to maintain a sufficient amount of iron in the water column for about three days between dosing.
I'm posting two photos. the first was after one week of using the root tab recipe and the second is 18 days later. Tremendous recovery. I wish I had taken a pic when it was at its worst.
Thanks so much for this thread. I really appreciate all the info and help.