New to this Forum. Need Help with Black Spots on Amaranthus Leaves. Please help. | New Gardeners | Commercial Hydroponics farming

Hi Sir,

My name is Baskar and from Chennai. I'm a regular reader of your blog. I'm doing terrace gardening and have planted Amaranthus Greens (Sirukeerai and Araikeerai in Tamil) in grow bags. I'm seeing black colour spots on top of the leaves. Also some web like thing is formed in some of the stems along with black spots. I have attached the photo as well. I'm using oil cakes from neem seeds (veppam punnakku in tamil) and Turmeric Water (manjal karaisal in Tamil) for this problem. Please advise a solution for this problem.

Thanks
Baskar