Okay, where do I begin? Your tank is well and truly overstocked. Your tank is just not big enough for the amount of fish you have got. Okay, You have got to test the water for ammonia, nitrite, nitrate and pH. Thi should have been the first thing you did before medicating the tank. Many illnesses are brought on when fish are stressed due to poor water conditions. Poor water conditions often arise when there are too many fish in the tank, like in your situation. . I would prefer to know what your water water conditions. If your water conditions are not good, then medicating the tank is fruitless.
It does rather sound like you added all these fish without cycling the tank, it's no wonder you started having problems from the word go. Popeye, is often brought on by poor water conditions, again, we need to know what your conditions before medicating. Medication don't work properly when conditions are poor in the tank. I would suggest that you increase your tank maintenance doing a small water change every other day making sure you use a water conditioner. Get yourself some test kits as soon as possible and test the water, make sure you do the nitrate test properly, read the instructions carefully, you will often get false readings if you don't shake the vile and bottles for long enough, the readings can often be zero. I've often seen people boasting that they don't have any nitrate in their tank, they then realise they haven't been doing the tests properly.
White spot can often be cleared up by increasing the tank temperature to 30°C and leaving it like that for 10 days. There's a very good section on the website which talks about website, read it very carefully
I would strongly advise you to reduce the amount of fish you having your tank. Did you know that pacu can reach 3 feet. Okay, they normally only get this big in the wild, however, I've seen them at nearly 2 feet in captivity, they are truly gigantic fish, totally unsuitable for most home aquariums. Your problems are only going to get worse as the fish get bigger.