Upon just putting it into your tank it would not have died from a lack of nutrients, regardless it should be able to survive quite well with only nitrates.
Did you purchase this commercially or get it from a friend/fellow reefer? My guesses at this point are either that the conditions from the tank it came from to yours were very different (I even acclimate macro-algae) and/or the interconnecting strands were broken....this is a big no-no as all caluerpa that is connected is actually one big cell and if broken it often can spell doom for the severed section.