It does seem odd that you would deprive it of what it needs most during veg, but you will find at the same time your clones root, it will start feeding on some of it's lower fan leaves and turning light green. This is the plant being forced to use it's own nutes to create new growth til roots are established. There are SOME foliar sprays that are great for cloning. This can help the overall health of your clones while you are waiting for roots.
A humidity dome will increase success rates, incase you're not already using one
PH is a big factor. Maintaining a proper 5.3-5.5 for hydro/aero cloners is vital
Adding some beneficial bacteria, vitamin b complex, AND/OR humic acid will greatly increase your chances of rooting, and if/when they do, those 3 supplements will help create a healthy root system with effecient nutrient uptake.