Guppy overfeeding Swim bladder disease?

I have 6 guppys and 1 Catfish Dwarf suckers in my 350 liter tank, one of my guppys are dead, another Guppy is swimming on its back, 2 of them are very fat, and only staying at one spot, so maybe I have over feed them, ore they have parasites?

I did put some new plants in a week ago, could the plants have had something on them that make them sick?

I put 12 grams Epsom salt in my 350 liters aquarium, and will not feed them for one day, and then I will feed them peas for 3 days, is this a good plan, ore what should I do next?

Water:
Kh : 18
GH : 20
Ph 8
Ammonia : 0
Nitrit : 0
Nitrat : 12

Temperature:
23 c

Here is a video I toke

 

Giving this a bump up for you hope our members can help you today

 

Giving this a bump up for you hope our members can help you today

thanks I had to kill one of my fish the one that was swimming on its back I couldn't stand it suffering anymore it was a hard choice =(

 

Should I dip them in salt water? would that help them?

 

The 4 guppys I have left, 2 of them is overweight, then 1 there is not overweight but is olso sick, and then I have 1 more there is not either overweight, and there is acting normal.

I did a salt bath whit epsom salt yesterday and today they are not improve, one of them is just laying on the bottom and almost not moving, should I kill it ore should I wait?

Also I have another guppy in my quarantine tank, it's acting totally normal and I have feedet as much as the others.

Whar should I do?

 

Sadly one of my guppyes was almost not moving, so I decided to euthanize it white Clove Oils, the another one there is also sick I have feedet it squash and peas again, but I don't think it will improve


But I still have one guppy, there is acting totally normal, so I don't know why it's not affected. :/

I got a bunch of plants and 5 Panda Corys, and 1 guppy in my quarantine aquarium, I'm going to move over when the it has been in there in a month, but now when I got sick fish, when can I move them over to my tank where the sick fish is in?

 

I just noticed there is some small white worms crawling on my glass is that parasites?
They are 1 to 2 millimetres long, should I be worried about them? and what can I do to get rid of them, rather than clean them away?