Hi all, we have a tutti bambino cozee co sleeping crib and the mattress is like a slab! I know they are supposed to be firm for safe sleeping, but this seems too hard. My little one is not a great sleeper, and after a 30min nap has a very red mark on her head from contact with the mattress. Does anyone know if there are sids safe mattress toppers available? With my eldest who is now 7 we used a blanket underneath the sheet, but I understand this is a big no no. Thanks.