well lets look at the issue - marijuana grows well from about 50-55 to 85°F, at 85F the grow slows as below 50F. grow stops at either below 45F or above 90F.
Now, if you clone on soil your target is to keep the soil at 80°F for fast root grow - now going by that a water temp around the same should be optimum as well in DWC/hydro grows.
why is your water so warm in the first place ISO? can't recall that you not in the northern hemisphere as well and most of us have still winter due to that
no really, do you have a fish tank heating now as well and that isn't temp controlled?