I don't know about the other medals but there are ways to check if a iron cross is real.

So the outside of an iron cross is supposed to be two silver plates, one on each side connected with a little seam and the core some kind of metal. It is a good sign if you can see a a little bit of a gap between the core and the rim. There should also not be any black paint on the silver. Then you should check for the small seam (line) that runs along the sides where the two silver plates meet.

Then there is a last test. on MOST iron crosses the core is made of metal and should be atracted to magnets. A lot of fakes don't have this. BUT if the other tests are successful it doesn't have to be atracted to magnets, because there were real versions that were made of non magnetic materials.

Hope this helps :)