Molly fish - URGENT!

[imamesshelpme]

I have a 20L tank which I am fully aware is not big enough for mollies. It has 2 molly fish, 3 super small baby platys and one super small baby bristlenose catfish. I am waiting on a delivery of a 80L tank and a filter.
Feeding Fish Science tropical granular food, but fed Hikari micro pellets due to gettimg baby fish, cleaning tank a few times a week.
One molly is unable to swim. She was 100% when I left this morning and ate this morning. Was at the bottom unable to swim and looks like she's breathing heavily when I got back. Also swimming in circles, or just loses control when she tries to swim hard enough. She's in a glass jar in a salt bath now.
Please help, what can I do to save her?? Might be worth noting she seems weaker than my other molly and always has been, health wise. Water changes have always helped, but I did a water change yesterday.

 

[coralbandit]

The fish looks very skinny?
Has it been eating regularly?
What made you think a salt bath would help? I would think measuring the right amount salt for such a small jar would be hard?
I am sorry if the fish has already passed, IMO it is not long lived if it has not yet.

 

[KFav93]

I can't view the video for some reason, but she may have swim bladder disease? I would try feeding her a frozen pea for the constipation. When they have swim bladder they are bloated and they barely swim. Then they can't control their body, it kind of floats around.

 

[Fresh2o]

OP - Upload your video to YouTube and post the link here.

 

[imamesshelpme]

The fish looks very skinny?
Has it been eating regularly?
What made you think a salt bath would help? I would think measuring the right amount salt for such a small jar would be hard?
I am sorry if the fish has already passed, IMO it is not long lived if it has not yet.

You know, I'd thought she was looking a little skinny a few weeks ago, but she was still happily swimming around and eating regularly so I didn't think much of it. I think she was quite skinny when I bought her, so I probably just have a really bad eye for which fish are the healthiest.
Also, I read up on this disease (can't think for the life of me what it was called) but it causes them to behave like they have swim bladder issues. Apparently salt baths help, and I was ready to try anything. And yes, measuring the salt was super hard. Had to look up guides online and make my best judgement. She perked up a lot in the salt bath.

Also she passed away last night. She managed to swim around a little, and then spent her final moments resting on a plant she was working on shredding to pieces.

In response to the other person who replied: I did feed her some pea, she went mad for it. But I don't understand why it would take her life so quickly?
I'm thinking either she wasn't able to eat enough, or since I've had a few deaths, possibly my nitrates are too high.