Plant height

Plants are living beings influenced by genetics, the shortest will probably remain the shortest (Try doing LST if the difference is too much), however your babies will get much taller during the transition period between vegetative and flowering, you will see what an explosion! Good luck :)

I wouldn’t mess with your light height - no. Couple of reasons (assuming all 3 are autos) -they’re gonna hit their stretch phase soon where they will grow vertically plenty and fill out much more. -autos from third party sellers like herbies are a roll of the dice on genetics. Honestly, most autos in general are a roll of the dice. Allow me to try to explain - these companies have bought these seeds from random breeders. They themselves do not breed. That’s hardly the point but keep that in mind. So autoflowers are normal canna bred with ruderalis canna for the singular trait of “autoflowering” or flowering automatically around 4-6 weeks in regardless of light cycle. This trait was found in ruderalis canna in Siberia. It adapted to those crazy daylight hours to flower without 12 hours darkness. This is not the only trait that it has compared to your standard cannabis sativa. It is often much shorter, much more stout, much tighter nodes, less apical growth, different leaf structure. These are just the obvious traits. Sooo, these companies breed a few generations deep just to hopefully stabilize the “auto” trait without any care for other traits.. because it’s recessive, that’s the way it is.. you can’t ask for too much when trying to keep the autoflower gene. So this means you end up with crazy mixes of the normal canna plant with ruderalis plant genetics.. some tall, some short, some medium. Some tight nodes some not.. all they tried to stabilize was the autoflower gene. To be honest, a lot of breeders can’t even get that far, you’ll see ppl all over the questions asking why their autoflower is still in Veg 12 weeks in. It’s because the breeders didn’t take the time to do things right. Unfortunately, this is the state of autoflowers still in cannabis.

And btw, I've just looked at the log you're keeping... you should track the pH and EC daily as well because those are the two MOST important measurements in any grow...