I know it takes a while for it to take effect, but I have seen it come and kill off fish without ANY symptoms during that time. They all seem to be optional "it might cause this, but it might not", sort of things. I'm on a betta forum right now talking to them about it. It could be a bunch of different things. I'm still treating him--using the leaves and salt. He's still alive today but not well. Gave him shallow water so he doesn't have to swim up to the top. A betta breeder told me I will know for sure in 4-6 days what it is--if it's an infection, it should clear up with the medication and I will see improvement at that time. Almost all other betta infections get better with clean warm water, epsom salt, and indian almond leaves. TB is one of the only ones that actually does not respond at all to this type of treatment.
Still hoping for the best, but preparing for the worst.