Are you keeping it well watered ? If its against a south facing wall,it will dry out very quickly,as the rain doesn't usually get to the roots.I throw my washing up water on mine.as well as watering it.

Another ploy to get an ailing shrub through a bad patch especially if it is dry. Cut the bottom off the largest lemonade plastic bottle you can find. remove the cap. Trowel a deep hole near the shrub root. Place 2 or 3 small stones in the hole. Up end the bottle in the hole and pour in your 2 litres straight to the root. If using washup water pour it on the soil. Yobs leave these bottles in the street for me!!

This could be Pyracantha scab, which is a fungal infection. It overwinters on infected leaves which remain on the plant, and as tiny pustules on the shoots. Check for evidence of these if you can and prune out severely infected areas, together with any twigs bearing the pustules. You can also try a spray - it used to be carbendazim, but probably that's been withdrawn, so check the Provado range, or other ranges of fungicides, for one that says it will treat this condition. This assumes that drought is not the problem - where you live, I'd have thought that unlikely, but its not impossible.

We get our fair of rain here too,but as it is in a rain shadow area,against a wall,
like mine,it does get very dry.but,as Bamboo says,you need to check out other possibilities too.Hope you manage to solve the problem...