I have what I think is bba on a couple of my dark leafed annubius in a heavily planted tank. Its dark green/black short furry hairs along the edges of the leaves. Read the advice in the planted section, but not sure why I've only got three out of say 40 plants affected, I don't have any "stem" plants, all annubias, crypts, swords, mosses, fern, vallis etc. The annubius are at various heights in the tank on bogwood. Now, I'm not sure of my co2 level as my drop checker, denerlle, showed a false reading as I discovered to my dismay 5 weeks ago. My ph had nose dived to 5, I had inadvertently knocked the co2 timer so it wasn't coming on. The drop checker stayed a nice bright green throughout! So I took it out. I didn't notice the co2 wasn't on as the diffuser is set up below the uplift to my external, to increase contact time. I've never been sure if this is a good idea or not, but seemed to work very well in the previous set up. Lighting is high from twin T5 with reflectors. I don't suspect dissolved organics as I filter through Purigen. I dose every other day with lush max, a complete fertilizer. Lighting is on for 7.5hrs, co2 5.5 hrs, both timed. Water changes are 20% twice weekly. Any suggestions pls? Thanks