Help! Dying Platy

One of my 4 adult platies has suddenly gone pale and listless, not eating. I am worried for her, but also for the other three and the 10-11 fry who don't have any symptoms yet. I think the affected platy is probably going to die , but I hope the others don't catch it too. It could be old age, but i bought the platies just 4 weeks ago. Please help me identify whats causing this and thanks for any help in advance.

Tank size:125liters or 27ish imp.gallons
pH:7.0-8.0
ammonia:0
nitrite:0
tank temp:27-28 degrees C

Fish Symptoms (include full description including lesion, color, location, fish behavior):No external visible symptoms, except she was suddenly very pale in color almost white. She is usually hiding behind the filter, sitting on the bottom of the tank in the sand under the filter or hiding in the rock cave. Swimming sort of tilted to one side. Listless behaviour and not coming out to eat. Just hiding most of the time. This morning when I was feeding she popped up a little but then went back down. She doesn't have clamped fins yet. No other fish have any symptoms yet.

Volume and Frequency of water changes: Weekly 20% changes

Chemical Additives or Media in your tank:Carbon in the filter, a little salt because i was using salt and heat treatment for ich 3 1/2 weeks ago (ich was from the stress of being bought and put in the tank).

Tank inhabitants:4 adult platies (1 male 3 females), 10-11 platy fry and some pest snails.

Recent additions to your tank (living or decoration): Platies-4 weeks ago and some more plants-2 weeks ago

Exposure to chemicals: None that I know of.

Digital Photos:



Thanks again for any help.

Iffles

anyone?

It sounds bacterial but need to ask some questions to rule other things out.

Does she look bloated or thin.
What does it look like when she goes to the toilet.
Any signs of flicking and rubbing.
What do you feed the fish.

Hi, thanks for your reply.
She looks slightly on the thin side, her poop was reddish and stringy (2 days ago because she doesn't eat so she doesn't go now), there are no signs of flicking or rubbing. I feed them freeze dried tubifex (Interpet), TetraMin Crisps and every three days or so roughly an eighth of an algae table (Nutrafin Max Spirulina algae tablets) for some variation.
Thanks again.

Did she lose weight due to not eating.
Do you feed any red foods.
Check her anus to see if its enlarged or red and inflamed.
Does she swim on her side.
Any worms prutruding from the anus.
Lost any fish to bent spines.
Does her tummy look sunken in.

It could be internal parasites and bacterial infection. Internal parasites cause bacterial infections.

Need to improve the fish diet with frozen foods like daphnia and brime shrimp and green veg.

Hi thanks for your speedy reply.
Yes she did lose weight after not eating. The TetraMin Crisps are multicoloured and some are red (others green or yellow), but other than that, no. Her anus is normal size, no worms, but there is now a clear thread like poop, clearish white about 5-7cm long. She swims a little tilted (about 10-15 degrees from vertical) and usually rests on the substrate now, often leaning against something (like decorations, tank glass). None of the fish have bent spines, and i haven't ever lost a fish to bent spines. Her stomach isn't caved in, but she's slimmer than before.
By the way, what sort of veg do you recommend?
Thanks

Ok.
I woud use a bacterial med. Not melafix.
Keep an eye on all fish for internal parasite signs.

Frozen daphnia good as it helps the fish digest its food.
Veg. You can feed lettuce, cucumba, broc, spinach, peas, sproats, green cabbage.

Anti internal bacteria med by interpet. But she dosn't sound good and the med might be to late.

Clear poo can mean the fish is running on empty.

Camallanus



Symptoms:

When the fish is stationary, deep red worms can be seen protruding from the anal pore. They are only visible when the fish is still because the worms retreat into the intestine at the fish’s slightest movement. Other signs may include an inflamed and enlarged anus. In severe infestations, the fish may become emaciated and spinal curvature may also occur.



Cause:

The parasitic worms Camallanus Cotti and Camallanus lacustris. These small, livebearing parasitic worms attach to the intestinal walls and rectum with pinchers. The worm’s grip is so tight that any attempts to remove it forcibly will rip away tissue from the intestinal wall. The worm’s pinching causes ischemia (reduced blood flow) to that part of the intestine. In time, the tissue to that part of the intestine will die, at which time the worm will migrate to another part of the intestine. This causes perforations throughout the intestine, which allows other pathogens to gain entry. If the fish is not treated, either the parasite or bacterial will kill the fish. Camallanus infestations occur most often in livebearing fish such as Guppies and Mollies, though infection is possible in all fish. Camallanus infestations are contagious. All fish, including those not yet showing visible symptoms, as well as the aquarium, should be treated.



Treatment:

Treat with Internal Parasite Guard, Pipzine, Disco-Worm, Trichlorfon or Fluke-Tabs as well as a medicated food to prevent a bacterial infection.

Thanks for your help, but she died last night . It must have been too late for her , but i'm hoping the others will be ok. Anyway, thanks again for your help.

So sorry,.
Bless her.
R.I.P.

Keep a look out for internal parasites signs.
Good Luck.

Thanks for your help though. Will look out for any parasites.