What's the make of the test kit you are using?
Bad water quality can make fish flick and rub. Also it can make them dart. Water quality is very good stats today are nitrate 5 nitrite 0 ammonia 0 PH 7.4
Are any of the fish laboured breathing, or gasping. NO
Has any chemicals gotten into the tank. NO
Have you added anything new to the tank like new fish, plants. Added some vialls but been in for 2 weeks
Have you changed declorinator. NO
Red inflamed anus can be dropsy, constipation, internal parasites.
Signs of internal parasites are as follows =
Long stringy white poo, clear mucas poo, red poo. NO
Worms sticking out of the anus. NO
Fish will look skinny or bloated. NO
Sunken in belly. NO
Bent spine. NO
Fish will sometimes swim on it's side. NO
Not eating and spitting food out. NO
Red inflamed anus, swollen, or enlarged anus. YES
Sometimes the fish will flick and rub. YES