Hi, why do the leaves on my courgettes and squash turn yellow and die? Thanks Deli.

This can be due to cold weather, especially if it has been wet, or it could be powdery mildew. Spray with a suitable disease spray to control powdery mildew. Regularly feed both plants with Tui Organic Seaweed Plant Tonic which stimulates root development and promotes healthy growth, along with enhancing flowering.