Suddenly my cakes won't rise

I have been baking for over 50 years and up till recently haven't had any real problems. The last two Victoria Sponges have failed to rise but I haven't changed either my method or ingredients. The only thing that has changed is that I had some Stork which was almost out of date so I froze it then thawed it out but they say that's ok to do could this be why? otherwise maybe I've just lost my touch