Nitrogen for leaves, potash for fruit and flowers, phosphate for roots. Magnesium and iron make the leaves nice and green.

Ammonium nitrate is a quickly absorbed nitrogen source, hoof and horn is slow release nitrogen (keratin breaks down slowly). Personally I would use a balanced fertiliser (NPK plus trace elements) to improve the general vigour.

Hi, welcome to GoY, whilst agreeing with the above, Pyracantha are not usually grown for the leaves, which can appear to be a bit sparse anyway, but for their flowers, and their later berries, so I wouldn't worry too much about the leaves, and just use a balanced fertilizer next spring, Derek.

Agree with Derek - something balanced like Growmore or Vitax Q4 will be fine, but don't fertilise now - do it next spring, as advised.