Thanks for the replies! It does seem to point to excessive iron dosing. But I've also read that Seachem Iron does not stay in the water column very long. Something to do with the nature of ferrous iron (is that chelated iron?). Anyway, here's some more details about my aquarium.
A little over one year old 50 gal. long ("breeder") tank. Lighting is two Kessil 360w Tuna Sun LEDs on 30% intensity and 30% color spectrum for 7 hours a day. Pressurized co2 provided with a Milwaukee regulator and a Milwaukee pH controller. co2 is only on during the 7 hour light period. I run the co2 off the Eheim canister through a Little Fishies Reactor and returns through a Lily Pipe. I also have a Seachem Tidal 110 HOB, as well as an Eheim 2217 canister filter. Substrate is about 3" of Carib Sea Eco Complete, with Dragon Stone and Spiderwood. Plants include The Water Wisteria - Hygrophila difformis (featured in the above pic), floating Water Sprite - Ceratopteris thalictroides, as well as some Monte Carlo carpet, and a few Onion Plants (name?).
Fish include 2 Bolivian Rams, an Electric Blue Ram, a nijsseni Apisto, a pair of Cockatoo Apistos, a Macmasteri Apisto, some Harlequin Rasboras, some Neon Tetras and a couple of Siamese Algae/Flying Foxes (which are getting too big). Other than that a few Amano Shrimp and some snails of unknown origin.
Dosing: I've been experimenting/testing many different ferts and additives and levels of each since the beginning. The last month or so this has developed into my own admittedly mad-scientist regimen of the following:
The week starts with:
Sun - 50% water water change. I add about a teaspoon of Seachem Equilibrium as well. I then dose 10ml of Thrive+ and and 5ml of Metricide 14 (Glutaraldehyde).
Mon. - 12 ml Seachem Trace, 5ml Metricide 14 (also was dosing 5ml of Seachem iron - which will be stopped)
Tues. - 5ml of Seachem Flourish comprehensive, 5ml Metricide 14
Wed. - 7 ml of Flourish Potassium, 5ml Metricide 14, (also was dosing 5ml of Seachem iron - which will be stopped)
Thurs. - about 10 ml of Dustin's Growth Juice (8 pumps), 5ml Metricede 14
Fri. - 12ml Seachem Trace, 5ml Metricede 14 & 5 ml Seachem Iron (the iron is being stopped now)
Sat. 7ml Seachem Potassium, 5ml Metricide 14.
Ammonia - 0, Nitrite - 0, Nitrate 10- 20, Gh was 1, as I've added Seachem Equilibrium, it's raised to 2. ph used to be 6.8-7. Between the co2 (although off at night) and and the Equilibrium, the day starts out at about 6.4 these days. I take it down to 5.7 with the pH controller. The drop checker shows green, the fish are happy.