poorly courgette

I've had real mixed results with my courgettes.
Most have gone great guns and are very prolific but one poorly specimin in a pot at the fornt of the house looks sickly.

A couple of phtoos here - any advice gratefully received! Am I overwatering it? Underfeeding it? Too much sunshine?

They are 'strato d'italia' and taste and look fab by the way.

healthy ones....


poorly one....