I am not sure if you are new to fish keeping in general, die off is something that may be a little more common in this hobby. Sometimes fish may die for various reasons and the same with corals. Panic and making a host of changes all at once could lead to more damage. I would suggest go back to the drawing board and understand your water better.and then figure out filtration and lighting.
Test PO4, NO3, Ammonia, Ph, Alk, Cal, Mag and Salinity. Test at a given time every day for a week just to understand what is going on with your water. Understand the uptake of these elements. And once you have this sorted, then get your testing to 2 times a week. Hanna checkers would be really good for the basics like NO3 High Range and PO4 ultra low range. Check if there are any swings in salinity,Ph, Alk, Cal. Are you using an RODI system, do you have a good resin for the Di phase, are you in a region where you can check metals in your water. This would be on the website of the company that handles water systems in your city or town,
Check you filtration, get the basics right with mech. Run activated carbon to help get rid of toxins or heavy metals that MAY be in the water. I actually use a canister filter and had it optimized to a point where my nitrates and phosphates bottomed out at 0 and messed up some soft corals. 0 nutrients is never a good thing. Corals are animals like all other animals that need nutrients to survive.
Finally your lighting, when your water is out of whack the lighting aint gonna fix that. So figure this out after you sorted out your water. I have not used Maxspect products so I will not comment on that. Different corals have different requirements so please read up on each coral that you put in your tank. Read up on placement, lighting, flow, nutrients to start of with. Forget about dosing at this stage, get the basics right. Go ahead and rent a PAR meter to help with placement options and always keep more that one placement option per coral so you can move them incase they aren't happy. If you have an app then make sure you set your levels based on the PAR and Placements and FORGET ABOUT IT. Do not keep changing that. I run AI Hydras and have an acclimation function, Check if you have that on your app. Personally I would get rid of moonlights till the tank has sort of settled in and give the corals some time without lights.
You can figure out flow in tandem with your lighting . These sorta go hand in hand for me. Flow is as important as lighing and optimising it to benefit most if not all should be the goal.
Lastly, if one coral is not happy and the others are thriving and real happy then do not change anything drastically to make that one coral happy. Just move it somewhere else and see how the flow and lighting affect it. Remember keep more that one placement option per coral in your tank.
Take it slow and sometimes you will deal with dead animals in this hobby. The main thing is to look after your water and if you got that down then that will look after your fish and corals. There is no overnight fixes in my opinion for both freshwater and saltwater aquariums.
