What potting compost is it in, it like Ericaceous soil for a start, likes a bit of shade on a hot sunny day, away from winds too, if in the ground it should not need feed I noticed Moon_grower saying once, if in a pot fork in some compost.
If you do give it some feed Apri/May time but no later :o))

Need more info and a photo if possible - is it in a pot? If it is, don't add garden compost to the pot unless your compost pile is turned a couple of times a week... usually the problem isn't related with feed - maybe its got die back, no idea without seeing it really.