Please help, DWC nutes question.

Ok so I'm totally new at this and I have searched throughout the forums and cannot find what I'm looking for but anyways, I've setup a nice lil spot and I need to know if I should just run straight clean water (good ph) in my dwc after transplanting my seedlings in rockwool or is it cool to keep a nutrient mix (at very mild levels) in my buckets the whole time until they get bigger and then upping the ppm's?
Again, sorry if I may be reposting a question similar tio this but I cannot find this basic of a topic.

Yeah, start with a very weak (less than 1/4 recommended) solution and work your way up.

I also add a little mag in the form of Epsom salt for the first couple weeks.

Ok, I was asking mainly because these G13 Haze seedlings are acting crazy. They strected a lot in a fish aquatium that I had setup so I moved them closer to the light and they stretched more, so I replanted them covering the long stems up with rock wool putting them into the dwc buckets. They are turning yellow and the funny thing is that the ph level is at 6.0 and the nutrients are one third of the strength.. What's goin on?

Here are the pics of two seedlings in two different media. Ones soil and ones dwc with hydroton.

Pics,
One in soil is even abit yellow.
https://db.tt/PwW3IHVy

And this one in dwc the leaves look burned or salted??
https://db.tt/Bbw1vZ86

Hopefully someone will give you more advice, but in my experiance I had trouble with my seedling/young plants turning yellow very early on in my DWC system.

since I started adding magnesium in the form of Epsom salt for the first 2 - 3 weeks, I don't have that problem anymore.

If they're turning yellow at that age and you're running DWC, then you're OVERNUTING. Just run plain water for the first 2-3 weeks. You can read my signature how I did it. Don't worry about ph until you start adding nutes -- the correct ph range is needed for nutrient absorption through the roots. Right now, the plants is taking what it needs from the cotyledons.

When you start adding nutes, you might want a strength even lighter than 1/4. Get a ppm meter. Your water will naturally have some ppms. Include that in the total count. My rule of thumb is 100 ppm for every week of age, starting around 3 weeks. So at 3 weeks, I want ppms of 300, including my water. At 8 weeks, it's 800ppm. And I stay there throughout flowering. Your plants will grow big and beautiful without damage.

Depending on your water's ppm level, you may need to add a bit of cal/mag to your nutes. My water's ppm level is 140, so I add a bit.

When you're adding nutes, keep the ph level between 5.6-5.8 if you can.

Good luck!