I don't know i just buy all bettas at any pet store.Well i don't even buy them for long time because somehow my bettas live long life. I have 8 of them. The oldest about 4 years old. All i do just 100% water changes for all of them . Never cycled my tanks tanks, well only because no one ever told me that. My first betta was gift and the instructions were full water changes:)
lovemyfish99 try to show the pictures. And if you think that it really fin rot you can definitely increase salt up to 3tsp/gall and treat him up to 14 days with daily water changes. But sometimes if the fin rot is very aggressive you might need medications.
Do not cross - contaminated anything between all your bettas, since fin rot is contagious.
For Steve if it just tail biting don't treat him with aquarium salt yet. Just keep water super clean to prevent infections. Is his tank also cycled? Also try may be put more toys, silk plants in his tank to distract him from the tail?
Your HM it ok to use the Epsom salt. I even read Oldfishlady wrote you can use it indefinitely in low doses and you don't have to do daily water changes. Are you overfeeding him?
Yes our little bettas get sick unfortunately:( But any animal do the same though.
I saw someone put tips for fishless and fishin cycling do you want me to find that link for you?