Resizing multiple frames in animatic

I’m working on an animatic, and have multiple frames on one drawing layer. I drew three of them too small compared to the rest, and want to resize them all to match the rest of the frames, but I want to resize all three of them by the same exact amount, without resizing the rest of the frames on this drawing layer. I can’t find any explanations on how to do this. Is there a way to do it?
I’ve tried moving them all to another layer, editing all the frames sizes, and then moving them back into the correct layer and for some reason they just snap back to the size they were before, and if i try to resize them individually in their own layer, I won’t get all three to be the same size. I can’t figure out what to do.