ID disease on melon leaves rough grey marking

Hi Guys, I'm a new gardner, this is my first time and I have a small patch going. So far I'm really enjoying it and learning by doing!

Firstly there are grey markings on the leaves of two of my melon plants on the top and underside. I'm not sure what this is. Initially I thought it was downy mildew but I dont think it is. I'd appreciate any help

Also, becuase I'm new to gardnening, I probably didn't space the plants out well enough so it looks like things are getting crowded. Im growing winter and summer squash, cucumbers, melons, pole beans and corn in west london. If you have any advice for me, I'd really apprecaite it. Thank you!

 

Hi John,

Thanks for your reply. Sorry I didn't mention this but there are no insects underneath and no stringy weby kind of material. It feels as if that grey stuff is part of the leaf or stuck on strongly.

I have whitefly on my apple tree and I managed to take care of that ok

 

yeah, the the top part is growing pretty well, I'll probably just leave it for now to see if anything changes and if I see any kind of spread I'll remove those leaves. Thanks for the help.

 

Not sure, but I think I've seen similar on marrows.
The leaf kind of gets a gap between the top layer and the bottom layer, leaves an air space that appears white or grey in spots on the leaves.
I dont think it does any harm and is normal.

 

Hi Pete,

Thats really interesting, I never thought it would be something that was part of the plant I just assumed it was something external.

Thanks for your explaination!