Wow... 7 fish in a 28g is a lot. Not a bad setup overall, but I would suggest finding a new home for the mandarin. They're a difficult to keep fish, and require a larger, well established tank. You may also want to cut the number of damsels down to 2. They get aggressive, and having four in a tank that size will become problematic over time.
You'll also want to cut your light time down considerably. Remember that even on the reef, you generally only get 12 hours of sunlight. I would say you're best bet is to cut back (1 hour a day or so) to about an 8 hour cycle. Keep in mind that your fish won't care what 8 hours you pick, so you can keep the lights on when you're going to be home to enjoy the tank, as long as you turn them on and off at the same time daily. (A cheap timer from Home Depot or Lowes makes this easy).
Otherwise, keep the table salt to your dinner table and you should be ok. Just keep reading and doing research.