2+ for PE mysis.. (slow thawed in cold tank water is the way to go)
Also, you should pick up some fresh table shrimp, squid, fish etc. and dice it up into a variety of sizes. Try to feed some fresh seafood at least once a week and you will see the results. Perhaps feeding your trigger heavily first and then targeting the tang would help. Also, you could use two separate basters to distract the trigger on one end of the tank and give the tang a chance to eat on the other.
How are you feeding the nori? it sounds like you are chopping it up and 'broadcast' feeding it to the whole tank.. If so, try using a piece of LR and with a rubberband to attach a half sheet (or so) of nori to it. That way your animals will be able to graze on it over a longer time period rather than having the dominant fish steal all of the food immediately.
Since it hasn't been recommended, soaking your food in a vitamin is not a bad idea. (selcon, vitachem etc)
San Francisco Bay's mysis are pathetic compared to PE. (nutritionally and visually) You will be glad you made the switch.
My vote would go to pellets over flake. Flake is messy and much of it ends up getting wasted. NLS (new life spectrum) make very popular pellets and they have a great ingredient list. I have been using Formula 2 (ocean nutrition) with good results too.