To me it sounds like what duddhamonk and Dav4 are suggesting. I did notice early in the spring soon after repotting that there were many, very small white flower like structures at many of the tips as well as the tips gradually going from a light brown/bronz, swelling, and then turning more brown as shown on the photo. I noted too that these were last years foliage only. There were many new shoots that did not do this. To mention again, the tree was nice and green all winter long, only doing this in late March/early April after repotting.