9.5 alk isn’t too high (I like to keep mine around 8.5), but it’s the stability that matters. A dkh between 7 and 12 is okay, you just need to pick a number (most people try to just stay where their salt mix mixes at), and then keep it stable. If the Alk is fluctuating or continually going down and then back up when you do a water change, it could absolutely stress your corals out to the point that they die. Your calcium and magnesium should also be stable, but fluctuations are a little less dangerous than they are with alk. Flow and lighting could also be the cause (or part of the cause, it could be a combination of things). One thing to keep in mind is that Scolys are all wild caught, so they don’t handle unstable water conditions as well as aquacultured pieces do. Acans are also usually wild caught and hammers and torches can be either, but this could be the reason why you’re seeing some corals do well and others dying.
You said your tank is new, which generally means that your parameters aren’t stable, I would wait to acquire any new corals until you’ve ensured your parameters are consistent. Start testing every day or every couple days and see how much they are fluctuating. Since you have several stony corals, you’ll probably need to start dosing a two part to keep your alk and calcium stable, but you won’t know (or how much to dose) until you have a log of how your parameters move over time.
