White guppy backs? What's going on?!

[redmare]

Here's the short version- fairly new guppies seemed "off" so I added salt, and now they have white backs but it's not fuzzy and doesn't match photos of columnaris but I'm not sure. 

Background- I had 3 male guppies living in my 30 gallon community, I've had them since mid November. They weren't fitting in very well so I decided to set them up their own tank with some girls and enjoy the fun of breeding guppies! My family just moved to a new town and while picking up some furniture from a lady in town, my mom noticed she had some spectacular guppies and so I went over to get some of hers to start the colony since they were well established and seemed very healthy, nothing had come or gone from the tank in over a year. I got one additional male, 2 juveniles, and 10 females from her, and set up a 27 gallon tank using cycled media for them. The cycled media wasn't quite up to the bioload of 16 ravenous guppies so I've been doing a bit of a fish-in cycle but all has been going well. 2 days in, the first batch of fry was born from the new females and I counted 13, and I still count 13 fry. They seem to be doing awesome. 

Parameters- pH 7.2, GH 7, KH 5, temp 78F, ammonia around 0.25 because of the fish in cycle, nitrite around 0.25 or less, nitrate 5-10. Filtered with an aquaclear 30 and a sponge filter rated for 40 gallons. Was planted until I started using salt, took most of the plants out. I have crushed coral on the way to raise the hardness. Gravel substrate, wood and rock semi aquascape.

Onto the issues- On the 29th I basically started to see something off with the guppies. A few of them seemed to have small nips in their pectoral fins, and the new male had clamped fins and was kind of lethargic. I also just kind of had a sense... That might be weird. I did a 70% water change and added 20 TBSP of aquarium salt (to 27 gallons). The next day I measured around 0.5 ammonia so did a 50% water change and re-dosed salt to the new water. January 1st I had to go out of town for a few days so I added some prime and hoped all would be well. When I got home yesterday (the 3rd) everyone looked awesome! They were so active and happy and their colours were popping like crazy, all the pectoral fins were whole again, and the male who was unwell was flaring his fins at the ladies and zipping around acting like a whole new fish! But then I noticed the white patches on some of their backs and got concerned all over again. I've attached a bunch of photos so you can try and get a sense of what I'm looking at. I also took 2 videos of the group to try and get the screenshots, I'll put those in too so you can see the whole group. It's just a few of the females with the patch, none of the males.

The one other caveat- I had gone to visit my cousin and he's a new hobbyist, so I brought my test kit with me to test his water. Of course, I forgot it there. I'm also out of aquarium salt. I can get both of these things again tomorrow afternoon. And also, I'm in Canada, so I don't have access to any of the good stuff. 

Thanks so much, all!

 

[Colu]

I  would treat for columnaris looking at pictures use aquarium salt 1table spoon for 2 gallons and maracyn2 columnaris is  highly infectious bacterial infection  

Edited January 5, 2021 by Colu

[redmare]

31 minutes ago, Colu said:

I  would treat for columnaris looking at pictures use aquarium salt 1table spoon for 2 gallons and maracyn columnaris is  highly infectious bacterial infection  

I've already got the salt in there and have no access to maracyn or other antibiotics in Canada

[redmare]

Another observation- the juveniles were picking at the back of the biggest female with some white. Not sure what this means. I'm minorly freaking out... I hate this part of the hobby.

[Colu]

Methylene blue can be use with aquarium salt  to help salt can work but it could take up 3/4weeks just need to  persevere

Edited January 5, 2021 by Colu

[redmare]

I went and bought new test kits and more salt- my ammonia was actually okay, just barely registered, but my nitrite was crazy high!! I was so worried about ammonia I forgot about nitrite. I changed 75% of the water and re-dosed salt to make it 1 TBSP per 2 gallons. After the change, Ammonia is 0 and nitrite is around 0.5, which I can live with. I'll do another big change tomorrow.