I have a new 55 gallon tank with plastic plants and a HOB Emperor Bio-Wheel filter. One month ago we put in 5 Harlequin Rasboras. We checked the water quality frequently and never had any readings other than completely normal. We've done two 25% water changes with gravel vacuum in the past month. Two weeks ago we bought 3 clown loaches. Even though they have several hiding places they've been very skittish and we don't see them for days at a time.
Yesterday we noticed that one of the clowns had ich. When we saw the other two we noticed they also were covered with the white spots. I did some quick research and bought some Maracide for the tank and administered the first dose (full strength). I have also increased the water temperature (it's currently at 83 and hopefully climbing -- heater is at max setting). I also took some water out of the tank to increase oxygen.
I have since done additional research and found conflicting advice saying :
Maracide is too hard on loaches, use at half strength.
Take the carbon out of the filter (package directions say this is unnecessary)
Add salt to the water, or some say this is too hard on loaches.
Don't add salt in addition to the medicine - others say this is okay.
I am so confused as to what to do next. Do I continue with the Maracide? Do I also add Maracyn or another anitibiotic? Do I add salt (special aquarium salt, or another kind)? Should I do a water change?
I don't know if I'm cut out for this. I was up half the night worrying about my loaches!

Here are my current readings: (my water is cloudy right now, perhaps I'm getting a bacteria bloom?). For the first time, they aren't quite normal.
Chlorine: 0
Nitrite: .5
Hardness: 250
pH: 8.0
Ammonia: 3.0+ (hard to tell exactly)
Any specific advice from an expert who's been through this would be appreciated!