Added new corals, torch expelling zooxanthellae

[Partially Submerged]

I added a trumpet coral and an acan along with two hitchhiker snails to my small tank (4g), and now - about 2 hours later, I am noticing that my torch coral (the only other LPS in the tank) is expelling zooxanthellae and has its tentacles retracted.

 

I am assuming this is a stress reaction. I am wondering what exactly the torch is reacting to. Can they sense other corals and does dislike the new corals? It's been peaceful so far. Or is it more likely reacting to the stress signals of new corals?

 

Edit: Oh, I am also noticing that my three snails have been sitting completely still for the last hour or so. Not sure if it's coincidence, and I know snails sometimes sit still for a while, but it's weird that they are all doing it at the same time. Should I prepare a water change? My anemone crab is behaving normally.

[Partially Submerged]

Torch is done misbehaving, and the snails are on the move again. I'd still be interested in your comments, of course.

[CronicReefer]

Did you pour any of the water from the store into your tank?

[Partially Submerged]

No, and I briefly rinsed the new corals with tap water.