Stunted Plant

Hi all, it's Newb again.

To make a long story short, (posted in another thread) I almost killed 3 of my 5 clones when I acquired them.
Since then I have nursed them back to health (with your help).
I have concerns about one of them, it just will not grow.
I maintain them all the same, except now, I'm gonna bud the larger ones.

My newly cut clones are as big as the small one.
Any Ideas on the problem and suggested solutions on how to get her to grow?

Thank You For Your Help

P.S.
Is Dr Hornsby's Big Bud any good for flowering?