It sounds like too much lime in the soil, or sometimes sodium will have the same effect. Was there recent concrete work done near the plant? Or maybe an icy walkway nearby needed more than the usual dose of salt? It might be a good idea to have the soil checked for pH--if it's too high, say much above 7, lime is the problem. Either way, the cure is organic matter, and the fastest treatment would be to make up a good batch of compost tea, and drench the soil with it. 1-3 cm of good compost laid on the soil around the bush would continue the treatment through next spring. If it is still trying to grow, the new leaves should soon start to come out normal green soon.