Hey crono, does your water contain the actual element sulfur or is it hydrogen sulfide and just smells like sulfur? Reason why I ask, sulfur can be filtered out with a filter but the hydrogen sulfide can't be filtered out since it's a gas; need an aerator for that.
If either applies, I wouldn't use the water. The plant does need sulfur, but only trace amounts of it. Increasing these amounts may cause nutrient lockout, in which case the place won't uptake any of the nutrients it needs to be healthy. My girls get only generic distilled water and I haven't had any problems at all with them. Hope this helps.
As for your seedlings, NO WAY. They're way to fragile at this point. Once they get 2 or 3 nodes going, you can try out 1/4 strength nutes, then 1/2, then once they're big enough you can give them the full amount.
Hit me up if you have any further questions