Can someone recommend meds from the UK which I can use to treat columnaris

[LemonGuy]

Recently, my female betta got mouth rot, and I've started to treat with https://www.petsathome.com/product/interpet-anti-fungus-and-fin-rot-aquarium-treatment-100ml/7122140P?productId=7122140&purchaseType=one-time&volume=100ml, as a dip treatment but according to some its harmful for fish so can someone recommend me some stuff!

This is her, she's barely an inch long and my first betta!

Edited June 29 by LemonGuy
Needed to add more info

[Colu]

Interpret antibacterial treatment isn't effective against Columnaris. Columnaris is a gram negative bacterial infections that spreads more quickly at temperatures over 75°f and can kill in 24hr to 7 days depending on the stain. the most effective treatment for columnaris is kanaplex and jungal fungus clear fizz tabs containing nitrofurazone combination of two medication provide a broad spectrum antibiotic treatment. as your the UK and it would take two long for that medication to arrive  What I would do is start treating with aquarium salt 1 table spoon for 1 gallon at that level of salt  will harm your plants and Esha 2000 I would treat in quarantine salt  is effective against columnaris at a high dose it  takes longer to work just remember to only put back in what you take out so if you do a 1 gallon water change put 1 table spoon of salt back in as salt only removed though water changes  I would also get holed of Sera bactopur direct tablets active ingredient is nifurpirinol a broad spectrum antibiotic treatment you should be able to get it   off eBay or Amazon  @LemonGuy

Edited June 30 by Colu