Hard to tell for sure, but looks like fuzz algae.
EI makes no such guarantee, seems you've misinterpreted something.
Excessive light intensity stresses plants, even at relatively short photoperiods. A stressed plant is unhealthy, even if it appears to be growing fast, and likely to grow algae. I see what appears to be val, crypts, and swords in your pictures - all of which will grow at low light levels, and are easier to stress.
2 x 20W CFLs over a 10G typically provide medium-high light, enough to grow anything. Despite a lot of the light being lost with CFLs. Poor reflectors, poor directionality so light escapes the tank sides instead of being thrown down, and the spiral shape itself causes much light to be absorbed by the bulb.
T5HO has none of these problems, and produces a lot more light per watt. Way too much light in this tank, unless the bulbs are significantly elevated.
I appreciate the elaboration! How would 1x18W fair better, then? I have DHG, Val, Crypts. java fern, and anubias in this tank. Would this 18W still give me the speed of growth I have right now? Also, how does fuzz hold up to H2O2? It's an aquatic life t5ho freshwater fixture with 1x18w 6500k and 1x18w rosette and is about 5" above the tank on its stands.