thefreedictionary.com has the following usage note under 'phenomenon':
Usage Note: Phenomenon is the only singular form of this noun; phenomena is the usual plural. Phenomenons may also be used as the plural in nonscientific writing when the meaning is "extraordinary things, occurrences, or persons": They were phenomenons in the history of music.
Perhaps then the tag 'phenomenons' should be renamed to 'phenomena'? I couldn't find a way to do that myself, I can only edit the wiki, not the tag name.