Fin rot treatment? HELP???

[bubbles87]

I am relatively new to fish keeping and have came across my first disease with my peppered corydora. I have been researching online and asked around a few pet shops what could be possibly wrong. My PH level is 6.4 everything else is at 0. I had first thought and was advised that it was swim bladder due to the fish leaning and falling to one side. I was then advised that it could be a bacterial/pestisite problem. Unfortunitly after coming home from seeking more advice I came in and one of the fish had died. When I took him out I noticed she had one red spot which brings me to why I now think its fin rot. I took the 2nd fish out who had only began to show signs today...well that I picked up on...so I could check it over properly and this one is worse with the red spots its mainly on its underneith. I also check over my other cory but she appears to be fine at this time. It seems only to have affected the 2 smaller corys, they are call only 10 months. I am now down to 2 corys 1 which is visably unwell and the other which appears to be fine at this time. I have a 48litre tank which only had 3 coeys so there is no way I had too many fish and my water readings seem to be pretty much spot on. Only thing I need to check is the water hardness but Im finding it hard to find somewhere that sells this so may need to order online. Im going to do a 10litre water change tomorrow when the water is ready. Ive also added anti white spot & parasite treatment as a pre causion but I fear this may have been the wrong thing as all I read is how u cant use so many different treatments with corys...so what can I use with them? I badly need help Im stuck...

Sorry if I have shared info that wasnt needed but I need your help and in a panic now

Any help will be much appreciated
Thanks

[CoryfanAad]

What are " everything else" ??? What temp you keep them. Did fins dissapear or were rotten? What do you feed them. Stop treating all kinds of disseases without diagnosing them first. It can be ammonia burning, it can be wrong food, it can be a bacteria in my opinion. Greetz Aad

[bubbles87]

Sorry what I meant by everything else is the ammonia, nitrite and nitrate levels. I am currently waiting on a API GH and KH Test Kit being delivered as I couldnt get one from any the pet shops round about me. Unfortunately I lost another cory today.
Temperature is at 24 degrees.
Im just not sure where to go from here, done a 10litre water change yesterday(I have a 48litre tank) Im thinking I should do another tomorrow? Any advice and guidance would be much appreciated

Thank you

What are " everything else" ??? What temp you keep them. Did fins dissapear or were rotten? What do you feed them. Stop treating all kinds of disseases without diagnosing them first. It can be ammonia burning, it can be wrong food, it can be a bacteria in my opinion. Greetz Aad

[CoryfanAad]

Ok, are they Peppered or Salt and pepper Corys?. For peppered the tank is too small to my believe. Ammonia and nitrite zero = perfect. Nitrate doesn't have to be zeroWhat do you feed them and what are the other fish in the tank? Waterchange always is a good thing. Greetz Aad

[mg7454]

Consider this: Saprolegnia
http://www.americanaquariumproducts.com/Columnaris.html

[CoryfanAad]

Very interesting article. Past it through. The redish belly isn't mentioned in it or is it? I understand more fungal-like white spots are symptoms of this disease. Or did i miss something. Super info though !!! Greetz Aad