Yeah, you can start pretty much straight away, but make sure you use a VERY weak nute mix, i.e: 1/4 - 1/3 of the recommended ratio. Alot of people just wait till their seedlings/clones are at least 2 weeks old/rooted before they start adding nutes to the water, but I've been slipping mine some, and they seem to like it
As you may have some nute burn, I'd just stick to water, or use a much weaker mix.. At the first sign of burn, stop using the nutes. At least in the quantity that was causing the problem, and NEVER give seedlings/new clones full strength... it's just asking for trouble. Kinda like giving a 5yr old a double jack daniels. Prepare for a disaster.
Good luck man!
Peace.