Took two seedlings and put them in soil. They seemed to be growing at a faster rate than the ones in the Hydro Planter. However, after some help from Lakeside Rob, I realized that I wasn't having the hydro planter pump the water/nutrients into the plants often enough (only twice a day to start). I've changed the timer to pump 12 times a day and the seedlings in the hydro planter are now growing much faster than the ones in the soil.

I am using the same water/nutrients from the hydro planter to water the seedlings in the soil.

Seedlings in soil:

Seedlings in the hydro planter (they really struggled when the hydro planter only pumped the water/nutrients/air twice a day). They are doing much beter now: