Welcome Ashley to PT,

Two weeks is such a short time, it can take cats up to 6 months to settle in properly.

I would seperate the cats now, placing the new cat in a spare room, to give them a break from each other.

They need to be introduced very very slowly and only under supervision. I wouldn't leave a new cat unsupervised with the established ones for at least a month maybe longer.

Best of luck with the feliway, I have heard good things about it.

Please bear in mind sometimes two cats won't get along together what ever you do, I consider the attack on Shadow as a very bad sign and how ever much you have bonded with Topper, Shadow was there first and deserves priority.

I hope things work out for you, I really do.

PS. We like photos of cats on this website. Hint Hint.