Light green & drooping -2 week young clone-

Hello all, hopefully someone can shine some light on an issue I'm having with a clone of mine, I'll try to give as descriptive as I can.

*STRAIN: Ultrasour by T.H. Seeds
*clone has been in soil for 1.5 weeks from when it rooted
*Indoor soil grow with FFOF
*watering with plain RO water ph'd to 6.5 (I wait until top inch or 2 is completely dry, then I water with about 1/4 gallon of RO water)
*600W HPS
*temps 77 during day and 69 during night
*light is about 2' above plant cannopy
*I have the plants topped and LST'd

MY THOUGHTS: I'm not sure as to what exactly the issue is with this clone, but I have them LST'd at about a 90 degree angle, and I topped them about a week ago. I also removed a few fan leaves on each plant. So maybe this specific clone is going through some simple stress from pruning? Or can it be a nutrient issue like a cal/mag deficiency?

I'm not sure what the issue could be here, I have 9 other clones of the same exact strain and age, and they are looking great:

Bummpppppppp, I just fed foliar with a calmag RO water..

Potassium Deficiency I would saay ! Does it look like this ?
Potassium isn't absorbed properly when there is too much calcium or nitrogen in the system. Check the pH of your water, and flush your whole system with water that contains half the normal amount of nutrients and see if your plant starts showing signs of improvement.

I haven't fed ant nutrients yet, since the clones are in FFOF. I am watering with RO water, so how could there be too much calcium and nitrogen?

In my opinion that stuff is way too strong to start off clones in. That's just my opinion though. If it works for you then so be it.

Ok so the clones are getting worse.. does this look like a cal/mag deficieny? I use RO water but I have NOT been adding calmag to the water.. just ph down to 7. Also, should I always water with straight 7 ph water or should I up it to 8 since FFOF comes hot with nutrients therefore it will be acidic soil?

The weird thing is that I have 10 clones total.. and it seems like half are all having the same issue (light green/yellow, drooping and brown spots. The other 5 clones are looking great, however! They are not drooping at all and a nice lime healthy green. I'm giving all the plants the same care so I am really stumped!

Bumppppppp

I use RO water ph'd to 7. My run off is usually around 5.5-6. I thought FFOF soil comes hot and with enough nutes to last clones 2-3 weeks? So could I be seeing a cal/mag deficiency since I'm not adding calmag+ to my RO water? I figured FFOF would have enough cal mag in it already to sustain healthy growth even without adding calmag+ to my RO wate

so in order for me to get soil ph at 6.5 or 6.8 I will need to adjust my water ph higher, right? Will it be ok to water with say a ph of 8 to accomodate the acidic soil?