Sunburn is not usually on the edges of the leaves. It sounds more like lack of water or fertilizer salts or possibly water with chemicals such as boron. Moving it when dormant is not usually a problem but it may not be the solution. Al

There is a big peony garden in the city. Last weekend I went to the garden and found that peony under trees is in better condition than that without any shading, the leafs under big trees is still fresh and green, the others have turn to yellow.
It is the best time now to move tree peony. Moving in this season is not that bad for peony if with some original soil around the root.