Scaling slices in Sprite Editor

I have a bunch sprites on one 1 1024 x 1024 texture file. If I increase the texture size to 2048 x 4096, the sprites I have already cut stay at the original resolution. So far it looks like you cannot select multiple slices. Is there a way to select multiple slices in the Sprite Editor and scale them up to match a new texture size? Or do I have to go in and re-slice everything by hand?