Whats wrong with my guppies?

[Christoffer]

I had 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, but killed it because it was suffering, 3 of them are very fat, and only staying at one spot.
1 of the 4 guppys is acting normal.

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


The 3 of them there is sick will not eat the peas im giving them, the one there is acting normal is eating it.


I did a salt bath whit epsom salt yesterday and today they are not improve


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

Do you guys know what is wrong whit them?


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


Temperature:
23 c


Here is a video i toke of them:

 

[alto]

Looking at the video, I would guess Columnaris as this is a significant issue in guppies and observed symptoms are consistent - I’d be surprised if any of the affected guppies survive

The one fellow swimming free in the tank may remain healthy - especially if the affected guppies are removed to an alternate tank

An epsom bath would be a poor choice if this is Columnaris, the bacterium thrives in harder water, more alkaline conditions

How long have you had these guppies?
Most guppies are commercially shipped with various medications, and can appear healthy for a couple weeks before beginning to show symptoms/losses; other times, the Columnaris can be very fast and aggressive with 90% mortality within a few days and almost no symptoms

Were the plants purchased from a plant only tank?

I would suggest to never purchase plants from a tank with guppies (Columnaris concern) or groups of Betta females (various Mycobacterium sp with incidence levels up to 70% in farm stocks), if only plants locally available are in mixed tanks, then remove all rock wool, soak and wash plant thoroughly before placing in your tank, do large daily water changes for several days
Or only purchase tissue culture plants such as Tropica 1-2-Grow, purchase any pot plants on same day of arrival (at shop to minimize exposure)

If by dwarf sucker catfish you mean Otocinclus, these also seem prone to apparent Columnaris, but survival rates are much better (they usually display some discolouration patches, and excess slime giving them a muted appearance, and are reluctant to move)