I left a chiffon I baked on the counter, wrapped in tin foil. And after 5~6 hours it shrank and became stiff. I thought maybe it's too warm and dry in the room(25 C, humidity around 35 %) so I put the next one I baked in the fridge. It became stiff anyway. And the similar thing happens to all other cakes involving whipping egg white, but not to store-bought cakes. Is it natural for cakes to shrink so fast? And is there something I can add to the cake to prevent this? We can hardly finish an 8-inch cake in one day!