Hi all, I have been swamped by life since I posted this. I will try some of your suggestions. Thank you for the responses.
Other clues based on the above:
I do have Eco-Complete in there.
Root tabs are replaced sporadically at best.
I use half tap water and half RO when I can.
I use the same substrate and water in a 10 gallon, and no trouble with diatoms there.
The lamps have been on the fixture for about a year now. May need replacing.
37 gallon community; 10 gallon S-SS CRS; 2x10 gallon guppies; Specialties: Japan blue guppies (wild type), Ginga sulfureus guppies, Blond platinum LS guppies with purple mutation.
Non-aquatics: Off-track thoroughbred racehorse; 2 Maine Coon-type cats; 2 fluffy house rabbits; 60 orchid plants.
12G Rimless Club