Magnesium deficiency shows itself from the edges first.

My best guess is that you need more Potassium in your plants' diet. It prevents fungal and bacterial attacks, which is what that kind of looks like.

Silicon and Calcium are also a good supplement.
stinkyattic Reviewed by stinkyattic on . lots of brown spots on leaves?? Hiya Folks and greetings from the hot and sunny Netherlands, Last week in growth of my five outdoor plants and one of them is showing some odd brown discolouring on its leaves. More and more leaves are affected every day and I'm a bit worried what might cause this. Hopefully some of you can shed some light on this problem! Many thanks, Happy C Rating: 5