Multiple Questions About Platy/swordtail Tank

[Kellene]

So about two weeks ago I bought three platys. A male and two females, of course. A week later, I bought three swordtails (a male and two females). I have a 45 gallon tank.
My male platy is being aggressive towards my male swordtail. I know that's normal, because they're both males, and the swordtail can out swim the platy. However, the male platy is also being aggressive to one of the female swordtails, but not the other. The female that is being bullied by the platy looks very much like the male, except she is yellow. (The two bullied swordtails are both Lyre tails) And now the yellow female has a white splotch on one of her pectoral fins. It doesn't seem to affect her swimming, and none of my other fish have a white splotch. I'm not entirely sure it's a disease. I do have aquarium salt in the tank, but only half of the recommended dose, just as a precaution.
Also concerning the male platy: he's not showing any interest in the female platys. I think they may be young (?) I had this same problem when I had platys last year. They never bred, and I got no fry
Lastly, my other female swordtail had a small batch of fry about 4 days ago. I saved three in a breeding net, and one is doing a very good job of surviving among the plants. How long before I can release the fry into the tank without worrying about them being eaten?
I apologize for writing so much, this is my first time with swordtails. Thank you for your time

 

[Mamashack]

 to TFF!
I have platies not swordtails but they are very similar and I believe can interbreed. Keep a very close eye on that white splotch, one spot alone is not conclusive, but since there's a lot of stress in that tank it could be ich (white spot) which is very contagious! If any more splotches appear on that fish or any of the others then that's what it probably is and the whole tank will need treating.

EDIT: Btw was your tank fully cycled before you added the fish? Are there any other fish in the tank other than the ones in your original post? It's not clear whether it's a new tank or an established one.

My fry have always been left in the main tank (survival of the fastest and fittest) and can outswim the adults at a week old. Basically they need to be big enough to not fit in an adult's mouth.

 

[Ny82]

I would agree with mamashak. I had an outbreak of ich when I first started the hobby. It started with one single spot on a femle guppies tail then spread like wildfire to everyone else. Can you post a picture? Ich on mine looked like a bit of fry food stuck to the tails. 
It might be fungal. Is it a spot or does it look fluffy? My descriptions are not very good lol. 
 
This pic is of my platy who had a fungal infection does it look like this?

 
Ich is tiny little white dots, I can't find a pic of when I had to deal with it but google it and you'll know.

 

[Kellene]

I've had problems with ich and fungal infections before in previous tanks...but they cleared right up after medication. I'm hesitant about medicating the tank yet because there are 7 live plants (annubias and watersprite), and I don't really know what's going on with that swordtail. :3
It's been two days since I first notice the spot, but no other fish are getting spots on their fins, and she still only has one spot. It's not fluffy. I don't know if I can get a pic, because you can only really see the spot straight-on. She doesn't seem to have any problems swimming though. I have already put in half of the recommended dose of aquarium salt last week before the spot showed up - as a precaution. Better too little than too much.
I know platys and swordtails can cross, but the male platy is chasing her the same way he chases the male swordtail - kind of like quickly charging at her but not pursuing. Should I temporarily remove the male platy or female swordtail?
There are two small cory catfish in the tank as well. I am ashamed to say that I did not cycle the tank (I know. Kellene, you're an idiot.) I've never cycled, and my fish actually live quite a long time. I've had fish in the tank for 3 weeks now, and no one is showing any signs of illness (minus the yellow female swordie) or poisoning.
Thank you for your advice

 

[snazy]

Water changes, water changes, water changes. ...
3 weeks is not even half cycle....
Careful with the salt and corys. They won't tolerate high levels but probably will be fine temporary with some salt as long as you melt it first and increase the dosage gradually.
 
Without a picture we can't say what your fish has or doesn't have. There are thousands of fish diseases and unfortunately one can be wrong each time what it is, as it's always just an educated guess.
I hope your fish do well through the cycle and none of them dies/gets sick.

 

[FishLover4+1]

You should probably buy a test kit to keep an eye on what's happening, saying that I never cycle a tank, I'm just carefully how many fish I add at once normally 1 a week till full and I don't test either, my mum won't buy me a test kit and I can't afford one. Keep an eye on the splodge too, my sisters goldfish turned white overnight so it could just be changing colour? I don't know just guessing good luck!!!

 

[Kellene]

Update: The yellow female swordtail still doesn't show any signs of illness - besides that white dot. She's zipping around the tank with the other two swordies - which makes me wonder if the dot on her fin could just be where her fin got nipped by the male platy. (Just an idea)
Speaking of the platy, yesterday he was just kind of hovering mid-water. Now he sits on the bottom or top of the tank. He looks washed-out, but all his fins are up. He has no spots. I've heard this could be a sign of stress, but he hasn't been getting harassed - he's been the one harassing. Could it be because of the Nitrogen cycle? All of the other fish are doing great, though. I'll do a large water change today and see if that helps.
Thanks for all of your advice