Early growth sick plants - photoperiod

This is probably the result of whe your pH went down to 4.7..........the damage will never go away or "heal" itself. Concentrate on the new growth and keeping everything stable now. Remember too, what is showing in the leaves today, is usually and indication of what happened in the root zone 10-14 days ago. The new growth seems ok, so I would not say it is a nutrition problem, but a previous pH problem......4.7 is extremely acidic and very cannabis unfriendly. Your current pH is fine, but a PPM of 450-600 at this age is probably safer.

Ok, so this is a photo... First of all, the GH Flora series needs to be equal amounts of the 3 parts... Grow, Micro, Bloom.... the feeding schedule is listed on every label so just follow that and adjust the EC while using that ratio... The ppm is probably a bit too high at their age and I would drop it to about 600. Dropping the pH-Down into the water probably burned some of the roots even though you brought it back up... and even if they weren't, such a wild swing in the pH is going to have adverse effect on the plants... If you need to add some more pH-Down to adjust it again, withdraw a gallon or so of water from you reservoir, add the pH-Down to that and take a reading of it and figure out how much that's going to bring your whole reservoir down. For example, I'm growing in DWC and each bucket has 3.5 gallons of water. If I withdraw one gallon from a bucket that's reading 6.4 and I want to get it to 5.8 (which is perfect for the age of your plants), I'll add enough pH-Down to that gallon to get it down to about 5.3, maybe even 5.2.... so adding 1 gallon of 5.2 to 2.5 gallons of 6.4, the result should be close enough to my goal to satisfy... And to RAISE the pH, I simply add some of my tap water which is naturally about 7.5... The more you work with this, the more you'll understand what YOUR system requires... Keeping the pH stable is going to be the best thing you can do for this grow at this point... and if you get the ratios of the nutes right, things should be just fine - just going to take some time... so have patience. DM me if you need any further help... Good luck....

is the lower part of stem green? if so may be light intensity.