Slow Grow problem

I started my second planet from a cutting on 12th May, i started feeding it until the roots was reaching out the pot and touching the water on 24th May.

The cutting was already topped but I topped it again and now it has 4 heads.. it's around 14 inch's in height coming to the end of it's 4th week..

But my friend who also had a cutting from the same crop as mine an who started his the same time as me, has a bigger planet..
He came around to mine to look at it and he said his one is almost twice as big as mine.. So I checked it out and he was right..

I was just wondering why? what do you guys think is wrong??

I've noticed the last few days the leaves on top are a lighter green than the ones on bottom plus a lot of the leaves are curling up a little.. I don't know what that means..

Any ideas?

They look hungry or like they would like more intense light.

Whats the ec/ppm of your solution?

I'm not to sure what you mean.. I'm using 'Canna Aqua Vega' at the moment.
I'm using 20ml A and 20ml B per 10L of water..
I've done everything right, even double checked everything when I did it.. The pH levels are 6.2 to 6.4 aswell..

I've had other friends say it looks hungry though..

Check your humidity.. if its below 50% try to get it above that at least preferably 60-80% while in veg.. if you added a source of humidity you can remove when the plant is large enough to create it own humidity.. so that you dont get rot in flower.. I use a swamp cooler and it substantially decreased veg time..

Your ph is a lil high try keeping it closer to 5.4-5.8.. and it definitely looks sick.. humidity and lowering ph might help.. but you might want to try changing out the water and decreasing the nutes a bit to see if that helps..

I saw those pictures and immediately thought the pH was too high. 5.4-5.9 and it should pick up.