I'm usually not concerned w/ same species, and many keep nem specific w/ multiples, especially BTA's.
The only time I ever had an issue was mixed species, LTA and crispa, and that spans a 33 year period of keeping anemone's, and they were directly up against each other as one moved.
I don't doubt chem warfare exists and can happen, but I don't see or hear much about it really, and I think my one time was from direct contact of mixed species.
BTA's I've had multiples touching and never saw an issue.
New to tank BTA's often split from what seems to be new tank/params, possible shock or stress, that's pretty common.
Of course this is just my own personal experience I'm sharing, and they are animals, so many things are possible, but I would not expect issues.
Touching, doing something that disturbs them, much like you'll see even euphyllia slime up from handling them would more likely trigger a response IMO