Does anyone know what might be wrong with this zucchini plant? It looks like it's only affecting the biggest leaf. I'm not sure whether it's a nutrient deficiency, too much nutrient, or too much light. I've checked the pH and the ppm and both are in range for zucchini.

I don't know if this is significant, but there's an odor coming from the plant, kind of like a metallic smell. If you touch the leaf and then sniff your hand, the smell gets transferred to your hand. Sounds strange but I've grown zucchini outdoors in the past without noticing something like this.

Would appreciate your input on this before it gets worse. Thanks!

BTW, the holes on the leaf are from dropping a piece of oaktag on it by accident and it tore the leaf (happened way before the leaf started changing color)

{{gwi:1017067}}