About 6 months the reason I’m asking now is how stable everything has been and the amount of growth I’ve been having recently. My first coral is a hammer that now has four heads and started with two, it split, and about six more are sproutingThere are a lot of IF's in that answer.
If you get a nem that is prone to walking, and if while walking it decides to sting things, and if it stings enough, and if the coral can't do anything about it, there's a chance it'll kill a coral.
I've got bta's tucked into and around coral. Only one that stings and even it hasn't killed anything. Just ticked off a few mushrooms.
Got one that does laps and never stings anything.
Personally I think the fear of BTA's around other coral is slightly overblown.
How long have you had the tank set up? I see more failure on here to Keep a BTA healthy in a young tank than I do about bta's killing coral, by probably 10x.