Hi Elise and welcome to GoY we need more info to help you. When did you plant? Is it in ground or pot? Shade full sun? Have you been watering? A photo would also be useful

The most likely cause of this is magnesium deficiency. Water every 3 weeks or so with a solution of epsom salts. 1 flat teaspoonful to 2 pints of water.

and needs an acid soil or ericaceous compost and rainwater

Sounds chlorotic - if you have it in a pot, give it an ericaceous feed (Miracle Gro make one called Rhododendron and Azalea feed). If its in the ground, buy some Sequestered Iron, mix according to the instructions and water onto the soil at the base of the plant.

Thanks for your help