How much should I lower it?I would say your water temp is too high
60's???!!! Dude, these are tropical reptiles.....they need higher temps. than tropical fish.I wouldn't heat water and keep it in 60's but provide a heat lamp over basking area.
I think it's about time for you to do some research and join a reptile forum. These are very simple basic things you are supposed to know BEFORE owning a reptile?How much should I lower it?
this is accurate, but you don't want them to go into brumation unless A.) you plan on breeding B.) in which case they are adults before brumating C.) temperatures remain under 56F for the duration of the 3 month brumation period.Aren't these actually found in nearly temperate climates and capable over wintering in freezing conditions. I personally don't keep reptiles but know at least that much. Take a look at this article by Darrel Barton.
http://www.wetwebmedia.com/FWSubWebIndex/RESCareBarton.htm
but you're also changing a good 90% of the water every week, if not more often. I'm not saying the water should be 80+, but 60's is way to low IMO. 72F is about the lowest you want it to drop, about the same you'd want it for most fishtanks. Basking lights only heat the top layer of water, just like sun....and it also depends on how much water you have in the tank. If you have a 100 watt light and only 6 inches of water it's one thing but if you have a 75 gallon tank 3/4 full and a floating log to bask, that's a HUGE difference.As long as your providing a heated basking area brumation would be prevented.
The point is there is no need to heat the water, in fact problems can arise from 80+ water temps.