Most of the soils are pre enriched and the nutrients last for approx 3 weeks , you are in the "no more nutrients" window but your plants are not showing any signs of deficiencies , and from what I know the plants under low light wattage like FL are consumming less nutrients than when they are under big wattage light ( google check that fact ) so I feel like the soil could fulfill them needs for a bit longer.
I would recommend to give nutrients when the 1st signs of deficiencies are showing , I mean when the 1st set of leaves ( bottom ) are starting to get a bit pale then it will be the perfect moment to start a feeding schedule