Hi!
The problem is how you use node “Random”.
Firstly you use it to get random coral and set static mesh:
Secondly, you use it to get size of random coral:
Problem is, there are two different calls of “Random” node. So coral you get when setting static mesh and coral you pick to get it’s size are two random corals, not the same one.
I recommend use “Random” node once, get all of it’s values (coral itself and it’s size) into variables and use them.