My first 4 Plants.

Going into week 3. As a newbie with no experience i have a golden rule, i will only use pH perfect coco grow and bloom at half dosage for all my grow, so i don't have to monitor pH levels. I have a carbon water filter on my sink. Also water to runoff, every 2-3 days so i don't get salt build up. Growing is normal i believe, 1 plant is lagging behind.. (orange sherbet) The lamp is 600watt full spectrum HID so 1 lamp for all my grow at 64cm at all times keeps temps at 26-28C. (gets to 30C if closer) Every time i water, the plants get a little droopy and back to normal for a day, is this normal? ALL COMMENTS APPRECIATED, NEED ADVICE, THANK YOU. :)