Sounds to me like they put the "Pink Stuff" right in the fresh water tank and simply pumped it from there to winterize.
Perhaps you need to start all over. Fill and drain your fresh water tank a couple more times. Flush your lines with city water hook up until you know it's completely clear. Leave the water heater in bypass. When you know the lines are clear with city water, then fill the fresh tank and pump from there. If still clear, then fill your water heater. If you get foamy water anywhere in this process, stop and flush the problem child (fresh tank needs flushed more, or maybe the water heater needs flushed more. Doing only one at a time like this will help identify where the problem is. But there is still antifreeze residual somewhere. Good luck.