Hey man how's it going. I just stumbled on this thread cuz i'm searching for other peoples' results on the Blueberry Gum. I'm on my first DWC as well and way ahead (day 40 or so of flower) so I'll be glad to try and post updates so you at least have an idea of what you can expect.
First though, I have some suggestions (kind suggestions, take them as you will):
System looks great. Thinking the burn on your leaves is likely due to
over feeding. Ladies this small don't need nutrients.. probably not for another week or even longer. In fact, plants still in their seedling stage usually do best from using trace nutrients (calcium, mag, etc.) in your tapwater. Since you're using RO water, as I do, you will want to look into a bottle of CALMAGto use with your system. In any case, if your system is just plain RO water or you even use a
tiny amount of nutrients right now, you won't really need to do any water changes. You should only start the weekly changes once there are enough nutes to build up in your system.
Your roots look healthy but they also look like they may have acquired some color already when ideally they should be nice and clear. What is the color of your water once the nutes are mixed? and you ph? and room temp? none of those should be an issue yet, i'm just nosey about your system.
In terms of your question about having a runt plant, i'll refer back to the plant being wayyyy too young. Once it really hits true vegetation it might turn into the monster.
Finally, your lighting--- you aren't using all those bulbs yet are you?? Plants that small won't even benefit from having one 100w equivalent CFL on them right now, and that's even overkill that can burn the plants. My veg cycle I started with 2 60w CFL until there were at least two sets of leaves then started using those 100w bulbs but all in all I doubt I ever used more than 5 100w through the entire veg and mine were over a foot tall before i flowered. Start small and once the ladies start putting on real growth then you'll wanna start adding more bulbs.
And raiderman, I'm a longtime soil grower and after making the conversion to hydro it's hard to look back. The difference in growth rate is phenomenal. However, DWC can be a buttload of work too so if you have the time and resources there are hydro setups that require much less maintenance with all the same payoff.
Hopefully you found these suggestions useful. Like I said I'm also on my first DWC cycle so these are just some of the tips and tricks i've picked up along the way. Feel free to hit me up with any questions and good luck on the grow!