Hi,
you need to abstract your system.
-- create your heart prefab as something that can work in any situation.
-- it has 3 gameobjects, one for each heart ( OR one gameobject with one texture with 3 hearts drawn in it)
-- create a global event "KILL" or something, that everytime it's called, decrease by 1 the heart counts, so you destroy one heart gamobject or switch the texture to the one with 2 hearts.
etc. Does that make sense?
bye,
Jean