It won't be looking its best at this time of year; pieris is grown for spring colour.
It could be that you are overwatering it - they prefer free draining acidic soil.

Is it in the ground or in a pot, and how long have you had the plant?

Any chance of a photograph? If not, is it just wilting or does it have any crispy brown leaves? Have you inspected all the stems and backs of leaves for signs of infestation or disease, anything that shouldn't be there?

It should be a bright, healthy looking green at the moment.

Mine is doing the same. No dead leaves, but it does look a bit sad with leaves that are quite pale. Our soil is on the edge of neutral but I'm still blaming the weather as I've grown it before on neutral soil with no problems.

My Pieris looked sad last year after flowering but come the spring looked healthy again with green leaves & lovely white lily of the valley looking flowers on it but it has all gone yukki again, ours is about 20yrs old, wonder what it will do next year?