What it's this ?

Looks like powdery mildew, which forms when plant foliage is dry, lighting is low, temperatures are moderate and there is high humidity and poor air circulation or a sick plant. If its only one leaf I would carefully use a plastic bag and remove it from the plant. Since its a fungus you don't want to be disturbing it and spreading the spores. Then treat it. I have read many different methods of treating and everyone prefers a different method. When the plant is budding then its even worse as you don't want to be spraying your buds. Some methods I have read are spraying the plant with( usually requires multiple applications). - H202 at a 3% concentration. - Milk ( 1 part milk, 2-3 parts water) - Organic Fungicide sprays - Neem oil <- Never use on buds!!!!

Buenas tardes Doudou3D, Efectivamente es moho. Antes de reducir la humedad en tu cultivo y mejorar la corriente de aire en él, personalmente quitaría las hojas afectadas con mucho cuidado de no contaminar las demás (dependiendo de lo grande que sea tu planta, claro) y aplicaria un fungicida (en los momentos de menos humedad del día). También vigilaría y buscaría los mismos sintomas en otras plantas que compartan espacio de cultivo y aplicaría el mismo método citado anteriormente. Espero no sea nada compañero. Mucho ánimo y suerte 💪

Hey that’s mold. I would check your humidity levels as if they are pretty high it will only continue to spread.

WPM... white powdery mold. I use hydrogen peroxide water mixture and spray the leaves (google for different uses) Going to need better air flow. I use a 8" oscillating fan.

Mold....