I planted this Daphne odora in 2013 and it has done well until a few months ago when I noticed a large section in the centre starting to wilt. Now that part is all brown, another section has begun to wilt as well. I have no reason to think it has been overwatered or underwatered so I hope someone who reads this can give me an idea what the problem may be and if there's anything I can do to halt it. I am going to take a few cuttings just in case. I did read that these daphnes live 10 t0 20 years; could it just be normal?