For starters, there seems to be a few things going on.
#1: Ick is a parasite caused by stress on the fish. That stress can be anything from temp. change, poor water quality (I'll get to that in a minute), harassment, PH difference, etc. The fact that these are new fish and they have it leads me to...
#2: Tiny white "bugs" ( copapods)on the glass are usually a symptom of an unclean aquarium. Your older fish have had the opportunity to get used to this dirtyness but the new fish were dumped right into it most likely stressing them out and causing the ick episode.
Assuming that the fish weren't sick when you bought them and that your fish weren't sick when you introduced these new fish into the tank, the "new" form of ick seems to be tolorant of a lot of the meds we used to use for treatment. That being said, a RAPID rise in temp of 4-6 degrees disturbs the parasite's natural cycle and helps the fish out. Assuming you keep your tank at 78-80 degrees, 4-6 degrees should land you around 86 degrees which the fish can handle. Using a copper based product like CopperSafe can help get rid of stubborn ick problems should temp alone not work. If possible, do a 20% water change and clean up some of the gravel area to try to clean up the detritus that the copapods are feeding on. Replace the water removed with 86 degree water.
Once healed, you want to make sure that you reduce the temp SLOWLY. No more than a 2 degree drop in a 24 hour time span. Too fast and you'll stress the fish out again and have a relapse. Once you've achieved a normal temp, get into the habit of doing a 10% water change weekly and clean a small portion of the gravel bed every other week to every 3rd week. You don't want to do too much at one time or else you'll disturb your bacteria bed. With a maintanence schedule like this, the water should never go bad unless you overfeed or over stock.
Finally, FYI, Maracyn and Maracyn 2 are antibiotics and will do nothing for the ick problem. Once the ick is cleared, they would be good to use to fight off any secondary infections from the parasites. Make sure you do a full treatment when using any antibiotics or you will create "super bugs" that will become immune to the meds (which is what I believe has happened with the Ick parasites). The parasite guard would be the only med of the three pictured that would have any effect on the Ick parasite.
Hope this all helps...