3rd grow, What's wrong with our plants?

[TrippyHippy]

This is our third grow. They are about 3 weeks old some are 2 weeks old and a runt. My bf and i don't know what's happening, the lower leaves are yellowing including some 2nd node leaves. This never happened before on our previous runs. They grew nicely while in seedling stage and still shooting new growth. Are we doing something wrong? I know they're quite stretchy, testing out a lower K MH and forgot to lower the lights.
We'll be topping them when they grow decent side branches.

They're in 1 gallon wide soft pots
Medium: Our own mix 7 parts washed coco, 2 perlite, 1 vermiculite, 1 worm castings, dolomite lime, GWS myco, humic acid
pH: 6.3-6.5 runoff, watered with 6.9 only when the pots feel light
RH: 55-65%
Temps: 26°C on, 20°C off
Nutes: Used only on 3 plants lucas formula GH Floranova Bloom(flushed first then fed) cause we thought they were hungry but nothing has changed so far.
Lighting: 400w metal halide

Anyone?:surrender:

 

[thehitman]

they look ok

 

[TrippyHippy]

they look ok

Quite worried. They don't look so good compared to our previous runs..

 

[c526]

high trippyhippy,great avatar I like that,lots

plants look alright
ph is good,RH is good

what I am seeing is you build a version of supersoil,not all of the ingredients,but a start
but then it says you also feed them a lucas formula,2 3 plants??

topping them now/soon promotes those side branches you are waiting for
the little leaves,always yellow,your end plant should not even have them on it by harvest.

remember plants are like people,none are the same,unless you use cuttings,each time could be different,so what worked in the last grow,for that particular species,may not work this time.