Stem Strength

After my seeds germinated I moved them into my aeroponic system. I read that using a fan in the beginning stages is important for stem strengthening. I started on low but one of the plants was bent over and now isn't standing tall. I turned the fan off and hoped that strength would come back over time. It hasn't straightened out. I moved the fan way back so that the fan would still move air around the room. I am about 2 weeks from when germination took place and the tertiary main leaves are now growing. I am using CFL at about 18000 lumens mix veg lighting. Starting very slow with the nutrients and will be upping to the full amount next week. 2 citral and 2 jock. the citral is the limp one. Thanks for your help.