Strange "pink stuff" freezing problem

I have three unopened gallons sitting in my car port. They were left over after winterizing the TT and motorhome. We have enjoyed temperatures in the negative teens this winter, and prompted by other threads on this subject I have periodically checked on those jugs. At no time have I found them anything but clear of ice. I've checked inside the camper, as well, and not seen any signs of slushing there. My old TT did not have a pick up tube with valve mounted to the pump, so I normally blew the lines dry and poured pink into the traps and toilet. This new TT has a pick up tube, so I drained the system then pumped pink all through the plumbing. I'm confident I'll have no problems when I dewinterize, but, of course, won't know for sure until I run water through the system.