Help...beginner With Sick Fish

Hi....we just started a 20G tank for my daughter with 2 mollies...a white one and a dalmation molly

prior to putting fish in we set the tank all up and let it do a fishless cycle for exactly 1 week

i had no salt in it and when we had the store test the water they said it was fine...i was given no numbers but was given the OK to put fish in the tank....

all was well until about 4 or 5 days ago when i noticed the white molly seemed to be laying on the bottom of the gravel quite a bit...she would still come up and eat heartily and everything but then i'd notice her right back down on the gravel again..the black one at this time was doing just fine

fast forward to yesterday and today i had been doing a little research and noticed she had some white spots sort of like ICH on her tailfin (i think it's a girl but not completely sure) so i turned up the heat gradually to 86 and added gradually some salt into the tank (which i now realize should have been in there the whole time to prevent it) ....per lots of forums saying this is the best treatment

well i also had noticed last night that the black one has white lips ...which is a sign of columnaris? I'm so confused as to how to treat these fish and get them better!! can someone give me some advice? they are both still eating fine

also i used a test strip and according to the color code the water is as follows:  using the TetraCare easy test strips

nitrate - 0
nitrite - 0
hardness (gh) - 75
chlorine - 0
total alkalinity - 50
ph - 7

again...these are just the test strips im gonna take a water sample back to the store and have them look again........if any of these numbers are off can you give me advice on how to adjust each one? I'm a beginner and feeling like an idiot LOL i just reallyyyyy dont want these fish to die cus my daughter loves them!:scry:

here are a few pictures showing what's going on....they aren't very good so here is a video too
 
http/www.youtube.com/watch?v=9MVHTLKWXak&feature=youtu.be

The problem is that your tank isn't 'cycled'; that means it doesn't have a colony of good bacteria living in the filter that eat the ammonia produced by the fish and turn it into less toxic substances; first nitrite, which is also toxic, and then nitrate, which is only toxic at very high levels, and which we keep low with water changes, in a cycled tank.
 
You need to do large water changes; get the 'crud' out as best you can until you can get a syphon tube; you can use a cut off piece of garden hose if you have any.
 
Drain the tank right down, leaving just enough water for the fish to swim upright (don't forget to switch your heater and filter off first!) before refilling with temperature matched, dechlorinated water.
 
Try and change at least 95% of the water right now; leave just enough water for the fish to swim upright (don't forget to switch your heater/filter off first!) before refiling with warmed, dechlorinated water. Then do 50 or 60% every day until you can afford some test kits of your own. If you do get the shop to test the water for you again, get them to write down the actual numbers for you.
 
Cut right back on feeding until your tank is cycled. Fish don't need much food, so a small pinch (all they can eat in two or three minutes) every other day would help. Don't worry, they won't starve!

Yes, everything that Fluttermoth said. If I had a dollar for every time I heard the LFS told someone that their tank can be cycled in a week and then advise to toss in a bunch of fish, I'd be a very wealthy woman.
 
When you do buy a test kit of your own (the sooner the better) make sure you get a liquid test kit with vials, such as API or Salifert or Nutrafin. Don't bother with test strips as they're wildly inaccurate.
 
But if you do follow the advice above, you might be able to save your fish, then follow the procedure for doing a "fish-in cycle" here: http/www.fishforums.net/index.php?/topic/277264-beginners-resource-center/
 
All sorts of resources can be found here. Good luck! And 

The black fish is a male, but the white one's fins were difficult to see so I can't tell the gender. The black one wasn't paying as much attention to it has he could/should if it was just in and a girl. Is the white one's anal fin fan shaped or does it look sort of like a stick like the black ones? If it's fan shaped then it is a she. 
 
 
In my opinion a 50% water change every other day would be enough, not necessarily daily as doing too many heavy water changes may stress the fish just as much as being in dirty water
 
You've already upped the temperature (In fact, you may have it a bit too high ) and added salt, how much salt have you added? Molly's are very tolerant of salt and in fact like it, so feel free to add the full amount recommended on the box. Also look into getting something like 'Jungle Ick Guard' To help get rid of the ick, it requires large water changes every few days so it will work well with you'r fish in cycle. It also turns your water blue  
 
As far as the mouth fungus you mentioned, it is caused by the same problems that caused the ick in your other fish, unfavorable water. It is a forum of columnaris,
It can be fatal unless treated early on. Kanacyn can treat the problem well. Erythromycin (By API) treats most bacterial infections, and works alright, but does not treat ick. 
 
I wouldn't use two different medications to treat these illnesses, I would try and cure the ick with salt and heat and look into treatment for the mouth fungus with a pharmaceutical.