Curling up has to do with overwatering / ph. I'm now at day 28 and they just got their first feeding, cal-mag has nitrogen content as well as your grow, so I 's take it easy on the nitrogen until they actually start yellowing. as well as your PH, 6.5-6.8 is the soil range, not 5.5. 5.5-5.8 is hydro. coco has natural acidic properties so 5.8-6.5 is your range so if you put in a low ph solution its only going to lower it, giving you a PHOS deficiency around week 3-4. focus on keeping the ph around 6.5 then wait till they start showing deficiencies. cal - mag was at week 2 half strength. I used my 3-2-2 fish and seaweed with it both at half strength and I have Nitrogen built up in my dark ass leaves, when they get bigger you will see them claw down telling you that they have too much N.
-steve
