if they are used to it every day then it shouldnt be a cause for any problems. 7 degrees is a little more than I would recommend, but I intentionally swing all of my systems 4-5 degrees daily and it surely isnt detrimental. In fact, I believe it not only makes them ship much better if you trade often, it also makes them much more resilient when something does go a little awry temp wise in your system.
If you are one to keep your temp at exactly the same temp all of the time, THEN swing it 7 degrees you could see some issues, but in the wild 6 degrees daily swing is commonplace and IMO is good to swing the temp a little every day in our systems.
If you have lots of pox going on, I would try to tighten that swing up a little but most importantly start treating all affected colonies until you get rid of it. Along side the furan (which should be used if you have the pox to any extent), good water quality and excellent flow will help you get a handle on the pox until you can find it no more