You don't have to suspect that you have red bugs, you can easily find out. I know you have a decent DSLR, you can use that to take some macros of your colonies. Zooming in will reveal the red bugs. Sometimes you can even see them without zooming in ! Tiny red specs on your colonies. Yes, I speak from experience.
And in my past experience, NO vet would ever give me interceptor. I tried LOTS. Even exotic pet vets in Calgary. They all turned me away. If I recall correctly you need(ed) a prescription (for your dog) for interceptor, so for you to walk in and ask for it for your fish tank is probably not kosher with that. I don't blame them, they are doctors after all.
I ended up obtaining interceptor from a friend who owned a dog. That's probably your best bet if they still sell interceptor. There are supposedly natural possibilities like pipefish.
When I had red bugs I had it for a long time and as Mindy said, it never caused STN in my colonies. It took me a long long time to find interceptor so just lived with it for a while and it was fine, I think. Just in case, I recommend setting up a prayer reactor.