Hi and welcome to the forum
Your fish do not have TB.
What is the ammonia, nitrite, nitrate, pH and GH of the water (in numbers)?
The pH and GH can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
How often do you clean the filter and how do you clean it?
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You shouldn't treat fish or any animal unless you know what the problem is. Anything that treats bacterial infections will also knock the filter bacteria around.
The following link has information about what to do if your fish get sick. It's long and boring but worth a read when you get some spare time.
https://www.fishforums.net/threads/what-to-do-if-your-fish-gets-sick.450268/
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Part of the guppy's intestine is sticking out of its butt. This normally goes back in after 24 hours but sometimes it doesn't. A bit of plant matter in its diet can help. Fasting the fish for a couple of days sometimes helps. If the above doesn't help, you can carefully catch the fish and run your finger very gently along its belly a couple of times. This can sometimes get the intestine to go back in but sometimes it doesn't. Be very careful doing this because you can injure the fish if you push the intestine too hard.
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The neon tetra looks like it has been attacked by something. How long has it looked like that?
If there is nothing big in the tank that tried to eat the neon tetra, then it probably has a bacterial and or protozoan infection.
A broad spectrum fish medication that treats bacterial, fungal and protozoan infections should clear it up assuming the fish doesn't die first.
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Fish do a stringy white poop for several reasons.
1) internal bacterial infection causes the fish to stop eating, swell up like a balloon, breath heavily at surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be cured because massive internal organ failure has already occurred.
2) internal protozoan infection cause the fish to lose weight rapidly (over a week or two), fish continues to eat and swim around but not as much as normal, does stringy white poop. If not treated the fish dies a week or so after these symptoms appear. Metronidazole normally works well for this.
The Californian government have listed Metronidazole as a carcinogen. That's a concern considering it was widely used to treat intestinal infections in people.
Anyway, handle with care, don't inhale the medication, and wash hands with soapy water after treating the fish or working in the tank.
3) intestinal worms like tapeworm and threadworms cause the fish to lose weight, continue eating and swimming normally, do a stringy white poop. Fish can do this for months and not be too badly affected. In some cases, fish with bad worm infestation will actually gain weight and get fat and look like a pregnant guppy. This is due to the huge number of worms inside the fish.
Livebearers like guppies, mollies, swordtails & platies are regularly infected with gill flukes and intestinal worms. If the fish are still eating well, then worms is the most likely cause.
You can use Praziquantel to treat tapeworm and gill flukes. And Levamisole to treat thread/ round worms. If these are not available, look for Flubendazole.
Remove carbon from filters before treatment and increase aeration/ surface turbulence to maximise oxygen levels in the water.
You treat the fish once a week for 3-4 weeks. The first treatment will kill any worms in the fish. The second and third treatments kill any baby worms that hatch from eggs inside the fish's digestive tract.
You do a 75% water change and complete gravel clean 24-48 hours after treatment. Clean the filter 24 hours after treatment too.
Treat every fish tank in the house at the same time.
Do not use the 2 medications together. If you want to treat both medications in a short space of time, use Praziquantel on day one. Do a 75% water change and gravel clean the substrate on day 2 & 3. Treat the tank with Levamisole on day 4 and do a 75% water change and gravel clean on day 5, 6 & 7 and then start with Praziquantel again on day 8.
The water changes will remove most of the medication so you don't overdose the fish. The gravel cleaning will suck out any worms and eggs that have been expelled by the fish. Repeating the treatment for 3-4 doses at weekly intervals will kill any worms that hatch from eggs. At the end of the treatment you will have healthier fish.