You can check the code I did here.
An individual flame clone disappears when hit by a water drop.
Just study the code to learn how it's done
And you can thank @seawolfwerehorse for inviting me to the discussion.
You don't have to change a variable for each clone either.
The clones already occupy different y positions when they move.
I check the y position of the clone when it's touched by the water drop.
I won't explain any further. You can check the code.
@Phase_Studios you wanted to make a Bloons td game a while back but you were afraid of how difficult it would be to code for clones to be destroyed. If you look at the code at the link i placed you'll see it's not that hard to make individual clones disappear.