Cichlids dying after large water change!!

I unfortunately had to remove about 90% of the water in my aquarium to move it on to a new stand & maybe I added water back too fast or missed a few drops of seachem prime in my new water which has led to most of my cichlids breathing hard while sitting at the bottom. It’s been two days now & some of them are swimming but I’ve noticed a bit of red coming from a few cichlid on their fins near their gills & my pleco seems to be shedding his slime coat which is alarming. All parameters have been reading good everyday including PH. Temp is good, oxygen is definitely fine as I have a wave maker/ air stone. Should I buy stress coat or maybe do a small 10% water change? It’s also been cycled for more than a year so it’s definitely not that. I’m all out of ideas & any help would be greatly appreciated!