have you waterd it enogh

Hi J79 and welcome to GoY. How long have you had the rhodo? What is your soil like acidic or alkaline? Where is it situated in your garden? If you could answer these questions we will be able to help you more.

But in short rhododendrons need to be planted in an acidic soil in semi shade. If this is not the case in your garden then you need to mulch heavily with ericaceaous compost and fork it in round the roots. Sequestered iron will help too.