Hey there, actually because of two things , first the lights are too close , second the humidity is too low. If the lights are too close the plant doesnt "stretch" that much. But growth rate itself is determined by VPD which is basically the relationship between temperature and humidity. Raise your humidity to 60/65%+ and you'll start seeing a big difference . Hope this helps ! 🚀
Balance in feeding in a crucial thing when growing Cannabis. I see a bit of nitro saturation and that will slow a lady down... Ladies can handle micro nutrients in higher amounts without negative effect but believe it or not. With half descent soil there is no need to add nutrients to your water for quite some time. I'm on 4th of growth with my lady in soil and there are quite a few misconceptions/common mistakes I'm seeing from the soil growing community and it's usually a matter of overcomplicating things. Cannabis has grown in soil for Millions of years...
Maybe it's because you're under LED, I know that with certain LEDs it can take longer. But don't worry, your plant is far from being done growing! During flowering, it will continue to grow. Happy growing 😊