I only clean my filter out once or twice a year. No need to do it usually unless the water flow is reduced.
The only way to know is to test the water. Can you tell us the pH, ammonia, nitrite and nitrate?
Also, how long has the tank been set up? I gather it has not been running for long (the 8months?)? What size is it and how many fish were in it and how many left?
I hope you did not mix your meds. Always only use one at a time and use carbon in between to make sure it has removed all the first med before adding another.
99% of problems are caused by poor, or incorrect, water conditions. White spot is also a sign of stress.