Possibly sick fish

I just set up my 75G two days ago. I used Bio-Spira so per the directions I added all the fish at once, including 6 female gouramis I bought at PetSmart (I know I should have quarantined them, but the only tank I had big enough to put them in was the 75 and I needed the full load to cycle with Bio-Spira). I knew I was taking a chance adding all the fish and not putting them in quarantine, but I hoped I would be OK. Looks like I was wrong. The gold gouramis initially showed streaks of blood at the base of their pectoral fins, but I wasn't sure if this was normal for thier coloration (I have tried finding good pics), since both had it and it seemed equal on both fins. Well now several of the opalines are showing the same streak of blood at the base of the pectoral fin and it isn't even on both fins and not all have it. Since I added fish and Bio-Spira at the same time I haven't done a water change yet because I needed to wait 48 hours for the bacteria to attach, so I will be doing a WC tonight. Water params are:

Ammonia - .25 ppm
Nitrite - .25 ppm
Nitrate - 5-10 ppm

I need to know what the blood at the base of the fins could be and how do I treat whatever it is. Full list of tank inhabitants is below:

3 male Opaline Gouramis
2 female Opaline Gouramis
2 female Gold Gouramis
2 female Blue Gouramis
3 Pictus Catfish
1 Albino Rainbow Shark
1 Spotted Pleco

Please help, I really don't want to lose this tank of fish! :help:

No, it is a line across the base of the pectoral fins. I thought ammonia, but it hasn't been above .25 at all, that is pretty low to cause damage that fast isn't it?

I will be doing a major water change very shortly (I have to wait for my hubby to come hoem to watch the two-year old). I just noticed that there is also a streak at the base of the tail on the biggest gold gourami. I have a bad feeling I may lose a lot of the fish in the tank.

I am frantically searching the internet, but we all know how that goes, it is very hard to figure out exactly what the problem is based on the fish disease sites. I prefer the real world experience people can give me here. But in the meantime I will keep searching.

OK, from what I have found it seems to be most likely either bacterial infection or parasites. Is there any medication that will treat both? Also I have 3 pictus cats in the tank and they are highly sensitive to medication.

If I wind up medicating the tank should I remove the fish that still look healthy or medicate the entire thing to make sure none of the other fish have the problem and it is just asymptomatic currently?

Going to try Maracyn 2, it seems to be the best bet as it is for septicemia, which causes blood streaking int he body adn I have now seen the blood in the tail and dorsal fins. Hopefully this will fix it, if not, guess I probably get to re-stock the tank

Off to pull apart my filters now to remove all the carbon, do a 50% water change and medicate. Should be done in a few hours - YUCK!