Why are the fan leaves darker than the rest?

I might be wuried about nothing ' but is my blue dream babys ok guys??
I've noticed a diFrench in texture and colour of my leaves?
So '' more details "yes"

Strain --blue dream

28 days from seed---(sprouted)

day/night
Temps--26c/20c

Lighting--2x marshydro 300 & 1x znet4 150--total power draw-360watt

Space-- 2.5x2.5x5ft grow tent

Ventilation--5"rkv&filter -- 4"tt inlet
1x 6"oscilating clipon fan

Pots/media-- 3gal square pots/plagron light mix

Nutrients -- growth technology range/formulex/grow/bloom/green fuse grow/cal-mag

Watering/feed scedual

300ml every other day weeks 1&2

Week 1&2-- formula 5ml litre

Weeks2&3-- grow 7ml / green fuse 1ml / calmag 1ml

500ml every other day weeks 3&4

Weeks3&4-- grow 7ml/ green fuse 1ml / calmag 1ml

I started them in a 5" pot and transplanted week 2 into a 3Gal square pot what will be the final pot size due to hight restrictions.

Also topped both plants at the 6th node, and once again 10 days later I topped in 2 diffrent top branch places.

They will be scrogg ed once they hit a desired hight? I think maybe around week 7veg from seed ' so in 3weeks.
Any advice would be amazing guys thanx!!

Plants look great. You seeing normal growth, as the fans are darker because they are the light gatherers, and the lighter leaves are just developing flowers and leaves. Nice plants, no problems

Yes the growth is normal I think ' I topped them and since I have seen new developing banniches and a little hight but ' I thought I might be getting a nitrogen problem due to the dark colour?

I'm planning on scrogg in these girls but I'm a little dubious because I'm not sure when to flip to 12/12 coz ' this blue dream likes the stretch 'apparently" ???

I'm a little ambitious on this one in terms of yeild because I pulled 5oz from 1 cheese I scrogg ed in this setup few months back ' with 80 watts less and I also flipped a little early so I won't be making that mistake again lol

Predicted --250g/280g
Wish me luck and thank you for your comments

Jimdamick is spot on! Was just watering my ladies this morning and noticed a few new girls have super dark fan leafs. Couldn't be happier!!!!