Posted: 20/08/2017 at 08:40
Try reducing the size of the picture to get it to load up.
Having said that it does sound like one of the Blackspot infections. Almost every plant has its own form of this. Some Quince (Cydonia cultivars) are more prone to it than others.
Not a lot one can do. Ours loses its leaves (collected up and burnt) in July most years and then grows a new set before normal leaf loss in autumn.
Poor fruiting this year for us was down to poor weather at flowering time, rather than the leaf spot.
If you could find a systemic fungicide, you could try that.