how did you test your water during the cycle if you don't have a test kit?
take some water to the lfs and have them test for everything. You could have something way off in the water. possibly ammonia
that is very possible that is a HUGE temp swing, you are lucky nothing else was effected. generally, you don't want the temp to swing more than 1-2 degrees max.
what size tank is this?
you really need to pick up some books on the hobby and read, this will give you a lot of info.