amquel causes more problems than it solves, it starves the bacteria of ammonia which kills them all which then kills your biological filtration making you have to cycle all over again. The best way to fight ammonia is to do water changes
Seriously, how about getting that PH way up? You keeping a freshwater or brackish tank? 7.8 is excellent for cichlids. I'd like to see it at 8.3 during the day and 8.1 at night. With that type of PH I'd bet money your ALK and CA are way off as well. Your coral will appreciate getting all of those params in order.
It very well may have been but you posted a ??? asking why your corals are closed up and in your params you list your PH as being very low.
it sounds like your tank is crashing and you need to figure out why. I've heard of trites and amm spiking while PH drastically falling due to a dead animal out of sight. So if nothing is dead or missing, maybe you have way overfed the tank?
unless it says kent marine on the bottle i would not put it in your water. Amquel will be so hard on your tank. saltwater tanks should never have them put in them. Do 1/3 water changes daily until you get them down. Is it a new tank?, are you getting nitrate spikes. It is normal for them to close and it is also normal for them to die in high ammonia and nitrate.