i dont know the specifics of your tank,,,, but I NEVER RECOMMEND TAKING THE FISH OUT FOR CLEANING. i dont even know why people would recommend this.
The best thing to do is clean the tank, with a sphyon and change aroune 25%-50% of the water and then add it back again with aged tap water with water conditioner.
by taking the fish out you add more stress than if you did the water change with the fish in the tank.
Either the water temperature was right, or you didnt acclimate them right, or the water wasnt correct.
But the problem is the directions your following... generally speaking most arent correct.