That doesn't sound good; they should be stronger than that. How long did you acclimate them?
Don't feed brine shrimp. It has no nutritional value to them. Feed frozen mysis.
The temperature is fine.
Your parameters seem fine. From the behavior you are describing, I was expecting readable ammonia or a low pH. They are definately reacting to something.
I would have put these seahorses in a bare bottom QT tank first, watched their poo and their eating habits, and de-wormed them prior to adding them to the display. You will need to set up a bare bottom QT tank to deworm these seahorses, since no one in the US is selling true CB Kuda, so they were more than likely pen-raised in the ocean and have come in with parasites. You cannot treat in the display tank because the meds will kill your biofiltration and any inverts in the display.