Some of the older leaves as well as new leaves are curling and turning brown. We have had a rather abnormal spring with not a whole lot of rain, and earlier than normal quite hot weather. Am I watering too much, too little or just what is going on?
Curling leaves can indicate pests or even disease.
Check for insects, though some can be difficult to see.
Coral Bells do need well draining soil. If the soil remained too wet and the roots suffered root rot, this could also present itself with dying leaves.
Neem Oil is a good treatment for most pests and even works as a fungicide.
Here are some links to help you.