How important is.

Distilled water in a Hydro setup? Im using tap and as soon as the roots hit the resevoir they started to turn brown (not a yellowish, but a true dark brown) the plants look alright although maybe a little stunted... I think it is either my water, or the res temp. I dont have a submercable thermometer yet. So will Tap water make my roots turn brown? or should I consider something else?

Tapwater doesn't harm my roots, it depends on where you live the quality of tap water you have available.

You can leave tap water out for 24 hours so that it will disperse the nasty chemicals that gov puts in there to control your brain

So here is a pic of the roots....