Fire Whip is put into the graveyard if you lose control of the creature since the card text says it can only enchant a creature you control.

Remember that you tap the creature as part of the cost of activating Fire Whip's granted ability. So, if you have two Fire Whips on a creature activating the first one will tap the creature, so you can't use the second one or any other ability which requires tapping the creature until you find a way to untap it.