I've spotted this 3 days ago on 2 different fan leaves. Never had mildew before. Looked at plenty of pictures and still can't quiet tell if it is in fact mildew or something else. Soil: FF ocean forest mixed with bat guano high in N, bat guano high in P, some dolomite lime and EWC. I let the soil sit for 6 weeks before I planted. Temps: 78-82 under 240w LED Humidity: 45-50% I've been just watering with de-chlorinated water and also used tea once, about 2 weeks ago. The tea had kelp meal, alfalfa meal and molasses, brewed for 24hrs. Here are the pics... Plant looks healthy otherwise. Just want to make sure it's not mildew.
Ya I got something exactly similar on one of my outdoor plants. I have no clue what it would be either. I don't think it's pm but yea couldn't tell ya, I'm interested to know
It doesn't look very much like PM to me. If you wipe the leaf, will it come off? With PM you can "wipe" it off the leaf or spray it with water and it will look like it's gone, but then it shows back up when the leaf dries. Since you first noticed it, has it spread at all? Could it be some kind of insect damage? What about mild heat/light stress? If it's not spreading and the new growth looks ok, I would just chalk it up to your girl being sassy and throwing a little "leaf funk" your way and wouldn't worry about it. HTH
It does not come off the leaves when swiped with finger. I think it's slowly getting larger on the two leaves I noticed it on. Maybe some kind of micro-nutrient deficiency?
Then I think we can safely say that it's not PM. Idk about a micro-nutrient deficiency. She looks healthy overall. You are in FFOF supplemented with guanos so it could be a micro problem. Do you have any kelp meal? That will solve your micro-nutrient problem, if in fact that's what it is. Make a FPE by soaking a few tablespoons of kelp in a gallon of water. After a day or two you can dilute it and use as a foliar feed, and give some the next time you water. If it is a micro problem that should fix it. Like I said earlier, it could just be a little bit of "leaf funk" that really doesn't amount to anything important. Might be a good idea to wait a few days and see what happens. But a top-dressing of kelp meal would be good for her overall and would ensure that she doesn't run into any micro problems in the future.