One possibility is that the plants are reaching, straining, for their light source. If you are using grow lights, put the plants closer to them. If you are not using grow lights, consider using them.
Lights are one possibility another is what are you feeding them. If you are using a fertilizer cut back on the nitrogen and increase the phosperous. Ideal phouspherous would read like 0-0-16. Also nip the tops on them spindleies and that will redirect the growth pattern from vertical to lateral. Hope this helps you out.
Sounds like to much nitrogen in the soil. Try increasing the Phospherous levels by using a fertilizer where the numbers read 0-0-16 0r some thing like that. Your description of the plants sound as if they “bolted” on you which cool weather crops can due if the soil temps increase suddenly for a day. Try prunning about and inc or so off the the tops . This will cause the plant to redirect growth to a lateral direction verses a vertical. Good luck and don’t give up!