You have got to be one of the most frustrating people I have ever met, and believe me when I say that this time it's taking me every ounce of self control I possess not to write every profane and offensive word in my vocabulary, hit Post and be done with you. I am trying to help you for the sake of your fish only, because I seriously doubt that anybody else will as we have learned the utter futility of giving you any advice.
I Cannot Believe that you left on holidays with sick fish in your tank and did nothing to try to help them, not even isolating them to prevent the spread of the disease. That rivals the stupidity of putting an oscar in a plastic bag because it behaved naturally - AFTER we had been telling you for two weeks to get rid of it.
It appears to me that you are essentially a person who doesn't give a #### about his fish. We have told you, time and time again, that the vast majority of the fish in your tank are unsuitable and need to be rehomed. Besides the fact that they grow too large and will be miserable if you try and keep them, several of them are predatory. Since you're capable of forming a cohesive sentence, I can't believe that you're honestly too stupid to understand when we tell you that the oscar and the eels WILL EAT YOUR OTHER FISH. They are PREDATORY. In the wild, that is what they do: they hunt down and kill other fish to eat. It is ludicrous to expect them to behave any differently because some selfish human comes along and puts them in a tank.
If you really wanted any of your fish to survive at all, or cared about them enough not to want them to have drawn out and painful deaths, then you would have done SOMETHING about trying to find new homes for them by now. It's been at least a month since people started telling you they needed to go, and since then, to my certain knowledge you have killed several mollies, several swordtails, two beautiful black ghost knives, and seriously, probably permanantly, harmed that oscar.
All in all, you seem to care far more about having exactly what you want in your tank and to hell with the fact that the fish are totally and utterly incompatible on a biological level. Right now, if you went to the local shop and bought six bottles of bleach and did a water change with them, it would be a more humane way to die than what you're currently doing to your fish. Any person who can treat an animal like this without making any effort to help it is seriously in my bad books, so I hope that you (and the moderators) forgive my bad language. I'm doing my best. I will try to refrain from ranting any more:
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Whitespot (ich) is an opportunistic disease. This means that it usually attacks fish that are already weakened, usually because they are stressed or have been sick with something else. It isn't hard to see why the mollies and swordtails would be stressed out in a tank that is ridiculously overstocked, almost certainly not cycled, and where they are chased around by several bloodthirsty predators who want to eat them.
Whitespot is a parasitic protozoan that burrows under the skin and feeds on teh blood of the fish. The flesh and skin that it's burrowed out goes white and sits on the surface as a spot. It can be killed by increasing the temperature of your tank considerably and adding a whitespot remedy. You're probably essentially screwed, because if you dose the medication at full rate you will kill the loach and remaining BGKF, but if you half dose it, then it's not going to fix the whitespot. My recommendation is that you remove the mollies into a hospital tank and treat them at full dosage there, but due to the sky-high stress levels of every single fish in that tank, and the ridiculous number of these parasites that will now be in the gravel (the midpoint of their lifecycle) due to you leaving sick fish in there until they died of the disease, you don't have much chance of preventing a full tank ich outbreak. If that happens - well I hope the fish die quickly, because it's probably kinder than what will happen to them living with you.
