Need help with white fungus and possible HITH

[Blazin]

I was gone for a little over a month and I learned that you can't trust other people to do any water changes while your gone the hard way. It seems like my siblings would only cap whatever water evaporated. When I came back from my trip I first went to my tank to see how my fish were doing. It seems like my red severum is not doing so well, he is swimming and eating just fine but doesn't looks good. He has a white spot on the right side of its body (seems like fungus) and a white spot on top of its lip (not on the lip, just above it. could this be early signs of HITH?). I did a massive water change (~80%) and plan on doing another one tomorrow morning. I also change the cartridges on one of my filters. I am running 2x Penguin 330s. I just finished doing some water test and these are my current params: Nitrate = 20, Nitrite = 0, and Ammonia = .5-1. I thought this was really unusually my ammonia is always at 0 could this be because of the massive water change and the change of the cartridges on one of my filters? How big of a water change do you guys suggest I should do next? Also should I get any meds to treat my fish?
I forgot to mention my tank is 55g and has a red severum, blue acara, 3 pictus, 4 giant danios, 2 odessa barbs, and a arulius barb. Once I find my camera I will post some pics

thank you for you help!

 

[Aquanero]

My guess would be you sent the thank into a mini cycle by changing the cartrige and doing an 80% water change at the same time. Add something like Seachem Stability or similar product to get some more nitrifying bacteria into the tank get it a couple of days to stablize before treating with any meds. Do another 25% water change tomorrow and redose with the bacteria. Test the water before the water change to see where the numbers are. The tank should settle in a couple of days.

 

[Blazin]

thank you for the advice!
so earlier today I did a 25% water change and added API Quick Start. I just tested my water again and these are the results:
Nitrate = looks closer to 10, Nitrite = 0, Ammonia = 0 - 0.25. My Ammonia is definitaly much lower than yesterday, I think I am going to do another 25% water change tomorrow again.
In addition to keeping my water clean, can I add anything to help curing the early stages of HITH?

 

[Blazin]

Here are some pictures I just took earlier today. It seems like the white fungus stuff he was growing on the side of his body is getting better (kinda hard to see but i circled it on the pic). As for the the white spot on top of his lips, that still looks the same.

 

[Aquanero]

Treat with some API General Cure or stright Metro if you can find it. You can also add salt at 1 tablespoon per 5 gallons of water. Make sure to remove any carbon if you use it. Also replace salt removed by any water changes.

 

[Blazin]

awesome i will go and see if i can find those at petco or petsmart near me. I have a sponge filter and 2 hob, both the hob use carbon cartridges. should i just remove those cartridges? will this cause any problems because there is nothing else in these filters but those cartridges.

 

[Aquanero]

It's possibile it could if that's all that's in there. If you treat and do the water changes you should be ok until finished. Just keep an eye on the water. These meds are not hard on nitrfuing bacteria.