Watering my cuttings

Hi guys, this is my second grow and i've had a few cuttings for over a week now. They are in compressed soil and about 3.5 inches tall. I've got 600w of light over them in a cool tube at about 1.5ft away. The roots look quality at about 3/4 of in inch long so i've moved them into 100mm rockwool blocks.
I really struggled with this part on my first go and i'm struggling this time too.
I'm wondering on your method of watering is at this stage?
As i say, the roots look great; bright white and hairy but the plants just look a bit weak/limp.
I'm not dosing any newts yet but my tap water is ladened with N & P. I have an RO unit, would i be best to impliment this now and control dosing myself, or, not bother dosing till they are a little more established?
I'll be using Auto Pots for the rest of the grow and Ionics A&B, Canna Boost, PK 13/14 and the addition of any deficient traces via my own dry powders.
Any help would be appreciated folks and i appolagise if it's been discussed before, i have had a good look before posting.
Cheers.

i use 300 ppm nutes before my seedlings even have roots. never had a problem. it would be cool to have a pic. make sure you are not overwatering as this will make your plants look limp

Thanks for the swift reply. Over watering my be an issue, i accidentally let them dry out when i had the light too close so now i may be a bit paranoid.
I'm dying to get some photos up, I've just been out and bought a new canon 40D with a sexy little 100mm macro lens, went to take some photos and the battery was flat, then i find out the freaking spanking new charger that came with is doesn't charge, gutted. New one on route so i'll get some up asap.

i know i overwatered mine as soon as i put them in my flood and drain. lol they looked pretty sick but bounced right back.