Pyracantha leaves turned bronze and brittle

I bought a pyracantha last summer which has done really well since then and remained shiny and healthy until a few weeks ago when the leaves became brittle and turned brown. I searched the root for disease but no sign of anything and the root seems healthy. I repotted to a very large pot in case the pot became too small but it still has not recovered. I had just started to feed again after winter and topped up the soil a little before it went downhill but otherwise I didn’t change it’s care in any way. It did not berry in winter but I didn’t mind as it was such a healthy looking plant. I also scraped a little off the bottom bark which still seems green and healthy. Can I save my beloved Pyracantha?