Looks like some sort of fungal infection, but I can't positively identify it.

well at the base of the leaf you have a lovely collection of aphids. they need getting rid of. if you go down the insecticide route make sure you use a formula designed for edibles. otherwise a soap spray will help.

Yep, a thorough spray with soapy water, getting all of the nooks and crannies, and/or ladybirds, if they are available. For prevention, planting plants with small flowers nearby will attract other beneficial insects, such as lacewings, hover flies, and tiny stingless wasps. Good flowers for that are yarrows, sweet alyssum, verbenas, scabious, viola tricolor hybrids, and various daisies.

Many thanks.

Apparently they are mealy aphids.

Same treatment, Canalhopper.

Thanks!