New 20 gallon tank - Not sure what the issue is

I have a 20 gallon that I set up 10 days ago. I used API stress coat and API stress zyme. I watied 5 days before adding any fish, I haven't changed the water yet, I think it might be too soon. The water was cloudy but cleared up after second dose of Stress zyme. Temperature is 78 or 79. I don't know the exact readings of anything else. I took water to PetSmart to be tested twice and was told both times that it was really good, all levels were appropriate. They only used the test strips.
I have a male betta, a balloon belly molly and a dalmation molly. They all eat all the food given to them, and I try very hard not to overfeed. Ive noticed the last couple of days that the mollies sort of peck at the decorations like they are looking for more food. They have always stayed together, sort of inspeparable. Now they swim apart from each other a lot of the time. The balloon belly has a sort of fungusy looking spot on the top of his head. Not at his mouth or anywhere else. He is orange in colour so this mark looks sort of like fluorescent orange mould. I don't recall seeing it before, but can't really be sure.
So I have a few of questions:
Should I get a general type of treatment since I don't know what it is? If so, what would I get?
Should I do a partial water change or is it too soon? They've only been in the tank for about 5 days.
Why are they pecking at the decorations? Stiil hungry? Something else wrong that I really don't know?
Any help would be appreciated. Thanks.

 

Do you know about the Nitrogen Cycle? Sounds like your tank didn't get cycled. That could be one of your biggest issues.

https://www.fishlore.com/NitrogenCycle.htm

 

Welcome to fishlore!

The first thing you should do is purchase a liquid test kit. I highly recommend the apI master test kit. A lot of people on here use it as well and it is much more accurate than those test strips. If that is what they are using at PetSmart then you are not getting an accurate reading of your water parameters.


I notice your profile says that you do know about the nitrogen cycle...but you put fish in within 5 days of filling the tank. Did you use TSS or any kind of bacteria starter when you added the fish? If not then I highly recommend a water change as the fish have been in there 5 days i'm sure there is ammonia by now that is harmful for the fish.

In most cases with fish illness pristine water conditions will allow the fish to heal on its own. By pristine I mean ammonia and nitrite both 0ppm and nitrates under 20ppm.

But like stated you really should get a liquid test kit to check for ammonia...and daily water changes will probably be in order until your tank is fully cycled.

 

Welcome to FL.

I think you might want to change the water, but I'm not sure 50% is good, I would do something like 30% but other members might think differently.

Did your ballon molly have the fungus when you bought it or did it just develop it recently? If you could you probably want to place it in a QT to keep the fungus from spreading.

An alternative is also you can buy are API fungus medication. You take out your filter and let the water run and add the package in there. It makes the water green but follow the instruction. However I'm not sure if it works or not but one fish that brings it in can cause problems with the tank. I'm currently going through it myself.

As for pecking, all mollies do that. They'll just peck at whatever they can. Don't worry about them not grouping.

 

I will get a test kit hopefully today, and hope it is more accurate than the strips used at the store. I do know about the nitrogen cycle, however I was informed that using the API stress coat and also the API stress zyme would make going through the whole thing for weeks unnecessary as it adds the bacteria immediately. Reading the information on it led me to the same belief. Am I incorrect and if so, what should I do now that I have 3 fish in the tank? I don't want to harm them, and using the stuff that I did, I figured they would be safe and the tank would cycle with their use.

Ok, I went to PetSmart and purchased a test kit. Results are:
PH 8.2
Ammonia 0.25
Nitrite 0
Nitrate 0

So the PH is too high and I guess the tank seems to be just starting to cycle? Or has it already and the ammonia just happens to be high now? I think the first assumption is correct.

Also I was told that the fish probably has Ich and I purchased medication, Sentry AQ Biospheres Maracide. It instructs to medicate on days 1, 3 and 5.

So my question now is this. Do I do a partial water change to lower the PH and the ammonia before adding the medication or just add it and not worry about the readings. Does doing any water changes during medication make it less effective? And if I lower the ammonia am I just prolonging the cycling process and affecting the fish for the worse?

As mentioned earlier, I have added API Stress Coat and API Stress Zyme as well. The stress zyme has been given 2 times so far.