Some custom ringtones can only be set as the main ringtone.

I am having a ringtone problem. I have created about 10 custom ringtones and put them on my iPhone 5. When I want to set my main ringtone ringer they are all available in the ringtone selection list. When I try to set some of them as a different ringtone (text tone, new email tone, reminder tone, etc) only 3 of my custom ringtones show up in the selection list. Very odd ....help please???