I have a Viollete de Bordeaux rooted last summer in a 1 gal pot. It is about 1 ft tall. It already put 3-4 leaves and it's trying to set 2 brebas (which I should remove). The problem is that the growing tip shriveled and dried out. The leaves are green and healthy, no sign of wilting or anything. What may cause the dying tip, and is it serious?