Let’s see the light … is it led , blurple or what.
Most seedlings can be at 20-24” … flouro lamps you can be hell of lot closer. Sometimes within inches .
No toothpicks or crutches . You can boost the rooting of buried stem by a light dusting of rooting powder around it as you transplant.
IF running a simple bagged potting soil mix , let that do the initial feeding upfront. Plant will become accustomed to its new home and not be overwhelmed by additional crap dumped on it at this point.
Since solo cup growing at this point kind of floundered, you can still get it to root out appropriately by burying exposed stalk.
Even a light Foliar of silica ( armorSI ) will boost the cellular strength and growth up front.
Ridiculously easy fix on your end.