Thank you!

What kind of markings? Is it sitting on the leaves like a deposit, or part of the tissue of the leaf itself? Need a photograph really.

The white markings are part of the leave itself, looks slightly mouldy.

thank you!

am wondering about powdery mildew, but without a photograph, could just as easily be damage from a grazing insect or even sunburn, from water droplets on the leaves when the sun is out.

Could be Leaf Miners too, a fairly common, though not serious pest of Sweet Peas....as Bamboo says, it depends what the markings look like.