Sounds like too much sun. Sunscald can turn the leaves yellow or bleach them. After a while, they will brown out if nothing is done. This usually occurs to the leaves in direct contact with the sunlight. Leaves located further inside the bush will remain green. If this is the case, you may need to provide the bush with more shade or consider tranplanting it.

The other time when you can see white leaves is when you apply winter protection techniques such as covering the bush with leaves or cardboard. If the bush breaks dormancy before the winter protection measures are removed, the shrub's leaves and stems that develop will not be able to use the sunlight to produce chlorophyll and will look white. Once the leaves are removed, the leaves turn green in a week or so on their own.