I think putting buds in the fridge is a bad idea. any moisture in the bud will freeze causing it to expand and damage everything from the bud to the cells in it. This includes THC and trpinoid cells, if totally dry then this should not happen however it is very hard to get your herb completely more than 97% dry. I think it was the fridge that brought down your potency, not the pipe. Either that or your tolerances went up.