help pink tailed trigger needs help

[=FC=Carbonizer]

I have a 77gal tank with 3 triggerfish, 1 lionfish,1 dwarf lion
i change 3.5 gallons of water twice a week

my pinktailed trigger is normally dark green, is now light green
almost whitish and has like white eyeshadow

when he swims its like his balance is off abit

please note i am new to salt tanks only had these guys
1 week

thanks in advance
les