[Munchkin]

Or was it mizuna? hmm anyway they're leafy greens and they're now mouldy  Not all of them on the same plant are mouldy. Has the rain made them mouldy?

[Springlands]

Probably a mixture of rain, warm weather and wind damage which has allowed the mould spores to develop. Also if you plant them too close together it can encourage mould. Try removing the mouldy leaves and you might find that the plants recover.

[Munchkin]

Ah they are pretty close together . Thanks for the info.