Whats going on here?

Hi.. see pics, please tell me whats going on if you have a clue. Stats follow!

Medium: 75% lightmix soil + 25% coco coir
Additives: 1 gram chalk per 1 Liter of soil (so i dont have to correct ph)
Pots: 18 Liter (4 gal?)
Temps light on: 27 degrees celcius (80f)
Temps light off: 19 degrees celclius (66f)
Humidity lamps on: 40-50%
Humidity lamps off: 50-65%
Age plants: 4 weeks from seed ( still in VEG phase 18/6)

Sofar i have not used any nutes, only root stimulator and GHE Diamond Nectar beacause they seem pretty dark green to me so i am affraid i will overfeed and burn tips.

Problem:
Leaf structure seems a bit squeezed together and growth seems to go slow suddenly.

Pictures:

1 is with HPS ON so detail is more visible
1 is with HPS OFF so you can see the color of the leaves good (flash was used)

flash isnt a good idea, they look fine if not under fed.

They do look fine to me.

I third they look ok.

4 weeks from seed? Wow!

They look marvellous! Id flip those pal lol!

Thanks.
I know they dont look bad but leaf structure used to be normal now they look a bit squeezed together (cant explain, pic tells more).
And growth seems stunned.

Shall i perhaps start feeding? Got GHE 3part here... I am not sure what strenght to start with..


Pa. I will flip them when my scrog-net is a bit more filled up.

What kind of lime did you use,and was it powdered?

BAC lime. Powdered yes

I was thinking you might not have added enough lime,as you havnt been checking your ph,
thats what could be wrong.Just a thought.

UPDATE:

I did a FloraKleen flush.. ohwell just 3L per pot until i got like 10-15% drain from what i've put in.
Now 36 hours later they look like brand new.. they started growing again and i can see they've spared quite some grow energy because they have grown about 3-4cm overnight, normally i wouldnt see that so easy but in a scrog its quite noticable as you can see the net suddenly looking a lot more filled.