Is this similar to what you're looking at?

Some of my parsley plants in the greenhouse have leaves with light-coloured blight at the tips. They got it when things became really stuffy and humid in there. I think it's a bacterial spot but not sure. Anyway, mine cleared up after I put the plants outside and allowed them to air out. This leaf is an older one I pulled off to show you but the new leaves don't have it.

It doesn't look to be quite the same as what you've got, but since you've got no other responses here I thought I'd throw this in there to see if that helps you in any way.