Colu

Can you take a picture of the sick any Redding to the edges of the fins

If she's still eating that good sign

With two air stones and a sponge filter the level of desloved oxygen in your tank should be fine it doesn't hurt to add another air stone during treatment I would treat with antibiotic treatment such as maracyn or maracyn2 that @nabokovfan87 suggested after one course of treatment give us an update over production of the slim coat can also be caused by external parasites I would also order some prazipro just to have it to hand just in case you need to follow up and a treat for a parasitic infection @zamMan

Do a round of kanaplex and then give us an update I would only treat your other tanks if your seeing any symptoms

It doesn't look good looks it looks like it lossed some weight how long have you had the Cory's before you notice symptoms any rapid breathing hanging out near the surface lethargy flashing spitting food sunken belly have you treated with any medication @zamMan

Grey Gill's can be an indication of nitire poisoning red Gill are a sign of ammonia poisoning possible permanent damage to the Gill's that's why your not seeing much improvement the peppered Cory that died were the spots raised or flat

So it would be difficult to lower the temperature without getting ac or getting a chiller unit for your tank in long run

Sorry to hear that at least to you did everything you could keep a very close eye on your remaining fish any symptoms start to treat straight away with kanaplex and jungal fungus clear fizz tabs

What's standing out is the temperature that's on the high side for kuhli loach it's possible your other fish have adapted to the higher temperatures the new loach died due to a combination of stress and high temperature is there any reason you you are keep you tank at 28-30 what I would do is gradually lower it to 25-26 higher temperatures also lower the levels of desloved oxygen so I would make sure you have plenty of surface agitation and add an extra air @Attack_muffin

Could be the start of mouth rot that can be associated with columnaris that a gram negative bacterial infections that spreads more quickly at temperatures over 75 and can kill in 24hr to 7 days depending on the stain I can't say for sure it's columnaris I would treat with a broad spectrum antibiotic such kanaplex if you notice them get worse than I would treat with kanaplex and jungal fungus clear fizz tabs containing nitrofurazone following this treatment plan @Elyse

If your still having issues after two weeks I would stop treating with metroplex have you seen any improvement while you have been treating with metroplex or noticed any rapid breathing hanging out near the surface lethargy flashing spitting food out sunken belly

The two spots aren't enough to concern me at the moment I would holed off on further treatment for now it's possible they have some damage to the Gill's caused by ammonia or nitrite as @nabokovfan87mention that's why your not seeing much improvement with the rapid breathing as it's been going on a month and the spots keep coming back to varying degrees it could also be stress related that why you keep having issues if your KH is dropping over time that will cause your pH to swing this can lead to stress see if you can get a good look at there Gill's to see if there grey or bright red grey

I Have kept and breed bristlenose in Temperature between 74-84 without any issues

What I would do is test daily and do a 50% water changes when every your detect any ammonia and add a double dose of prime to help detoxify any ammonia or nitrite till they constantly stay at zero

You can use maracyn that predominantly treats gram positive and some gram negative bacterial infection maracyn2 and kanaplex are more broad spectrum antibiotic treatment that predominantly treat gram negative some gram positive bacterial infections gram negative bacterial infections are most common type of bacterial infection found in fish

You can get parasites in the water around the shell of snails they can act as an intermediate host usually you need birds fish and snails to complete the live cycle

Medication can be hard on healthy fish so I would always quarantine if you can't get maracyn2 then I would treat with kanaplex there's always possibility that the antibiotic treatment will harm your benefial bacterial in the main tank

Could be inflammation of tissue caused by a bacterial infections or injury what I would do is quarantine if you can and do a course of maracyn2 and add a small amount of aquarium salt 1 table spoon for 5 gallons that will help reduce some of the inflammation @Elodie Rose

Have you got a side on picture of lump

I don't use north fin if you want a more natural diet repashy super green or solient green are great and tropical plecos tablet have 36% spirulina or tropical hi-algae discs contain 52% algae from 5 different types of algae their larger wafers you can break them up or EBo spirulina tabs contain 30% spirulina EBo veg sticks are 50%pumpkin 50%pea fibra and cucumber or blanched lettuce or spinach is what a feed my plecos that require a high percentage plant and algae based diet

All depends on how she progressing after the 5 days do a 50% water change and run active carbon for 24hr to remove any remaining medication and follow up with a second course of kanaplex and jungal fungus clear if your not seeing much improvement

It can take a couple of weeks to fully heal even after successful treatment it's important to monitor for at least 4 weeks to make sure the infection is dealt with before adding it back to main tank to avoid any potential issues further down the line @Teacups

If your quarantine tank isn't cycled you can have an extra sponge filter running in your main to add to your quarantine tank that's what I do than I can add some cycle media to quarantine tank I would feed a small amount once a day or every other day and keep a very close eye on your water parameters if you detect any ammonia or nitrite do a large water change and add a double dose of prime to help detoxify any ammonia or nitrite

Yes it's the way I would have quarantine for 20 plus years worked well for me

Have seen these lumps before they respond well to a small amount of aquarium salt 1 table spoon for 6 gallons salt as that level shouldn't harm your plants and add some Indian almond leaves as they have antibacterial and antifungal properties @Alex B