Ok an update on my chromis'. It's a good news/bad news kind of day.
The good news first. The one that was all stressed out last night made it through the night is now back to his same old self. He's swimming in his usual spots again.
And the bad news. The smallest of them died a little bit ago. He was quite small and I'm guessing that he was having a harder time dealing with the stress.

He was fine this morning but then when I got home from work, he couldn't swim straight and his breathing was quite laboured. He made it maybe another 30 minutes before dieing.
My lesson learned from this....stay away from them if they're still babies. I'm going to try and get ones are a little bigger and can take the stress of a new tank a little better.