Hi steph. If I were you I would just try to hold out on the meds especially of you can't be sure what exactly you are treating for. If you are worried about a parasite then my first steps would be to increase tank maintenance interval. I'm not saying that you have a dirty tank but the less stressed a fish is the less susceptible to disease they are. I would try to keep temperature around 25 degrees adjusted slowly. If you are leaving lights on for 10 hours or more I personally would reduce this to about 6-8. I would then rinse out my filter media in tank water and vac gravel every week. I would then change 50% water twice a week. It's amazing how just increasing water maintenance can improve fish condition. If there is no improvement following this I would them start looking at meds.
Meds can sometime be stressful to fish. But other times you have no option. I have been guilty of putting too many meds in my tank. I had columnaris that was caused by unhealthy water quality and feeding a poor quality fish flake which was also out of date
I would toss the flakes on the floor of the tank to ensure my Cory's were eating. Even though water parameters remained stable the excess food decreased water quality and poor diet and external stress from fish opened them up to columnaris. I lost a few fish but I put the loss of my ottos and Cory's down to the meds. I scrapped the meds and bought a quality fish flake such as new life spectrum or omega one. I then proceeded to drastically improve my tank maintenance. I haven't lost a fish since.
The columnaris has took it's toll on my GBR but he made it through and I was certain he would die. Now he is ok.
I'm just saying meds are in my opinion a last resort.