Yea it might abit stress and I actually transfer them from 5ft to 3ft qt...but normally if the fishes is eating and stable for year jus transfer them out with the main tank water parameter together into the qt would not harm them much, just add medicine to the qt will do...and some minor like pale or stress sign or 1 or 2 dot white spot will shown on fish sometime so this is the best time to check out it fishes wat is happening... And lastly important thing is use less the dosage of full treatment to treat them and 2 weeks time is enough for all check up.