I'm making a temporary garden for a client at home to move to the landscaping location. He requested his garden contain broccoli which is the plant I'm worried about currently. It seems to have grey patches on a single leaf at the moment.
I'm living in Australia and we are currently going through winter, minimum 2° celcius (35° fahrenheit) nights and 8° celcius (46° fahrenheit) days.
Here is the broccoli leaf: