Can someone plz tell me whats wrong with my plants ??!!

Hi i am a new grower and am having a little problem trying to find out what is wrong with my plants!!

My plants are just over 3 weeks old (from cuttings ) and stand about 22" tall , im growing in a grow tent , Ussing a 600watt dual spetrum light, with a 4" carbon filter and fan , and 4" ducting from in the tent to outside attached to a fan for fresh air , Im growing in playgron grow mix with pelite ph of the soil i believe is 5.8 -6.3 , .. The temps in the room are 79-82 rh 40-50% day and night is 62-65 rh 50-60%, I have the light about 2ft from tips , I ph the water at 6.3 , run off comes out at 6.7

The problem i have is that the leaves are very droopy just like they are clawing and going a very light green , I have not yet feed the palnts as the soil has enough to cover the feed for up to a month , ive been watering when the pots go quite light in waight and when the soil looks very dry , I have also noticed that there are a couple of leaves that have brown dots on (only 1 leaf and has about 4 dots next to each other) and on the other leaf they are white ans about the same amount,.. I have been misting the plants quite a bit latey with some canna rhizotnic npk 0.6-0.2-0.6 for stress , advised by my local store so that might be the problem with the spots ? i have looked for mights but can not find anything !

I did feed two plant's last night with a drop of superthrive and 1ml of aqua bloom to see if they would pic up , and no change as of yet ,

could anyone plaz help me