Hi, In the photo it looks so close to the house, is it under the eaves? Is it getting enough water? That spot can be pretty dry on many houses. The coffee grounds are not going to really change the pH of the soil if yours is too alkaline for rhododendrons. I would suggest getting a soil test from your local cooperative extension. If you tell them that you are growing rhododendrons they will tell you how should amend the soil. Also if this shrub has been neglected for awhile it will take more than a single season to get it back in shape. The flower is a good sign that you are on the right track. Good luck.