Is it his:
Blumeria graminis is a fungus that causes powdery mildew on grasses, including cereals (called barley powdery mildew or corn mildew). It is the only species in the genus Blumeria. It has also been called Erysiphe graminis and (by its anamorph) Oidium monilioides or Oidium tritici...
Hello,
I see that you give your plants extra nutrients such as nitrogen. I would advise you not to do that, especially not in such a small pot. I live close to holland and all the nutrients sold are exaggerated in termes of quantity. If the bottle sais put 1ml of nutrient for 10 l of water...