Remember that with LED lighting we want warmer canopy temperatures than we do under HPS. HPS puts out about 60% of it's photons in the infrared area, IR light warms surfaces it touches (leaves). To achieve optimal leaf surface temperatures under LED lighting we need a canopy temperature up around 83 - 86F where under HPS we might aim for 79F.
Cool leaf surface temperatures will slow the growth rate, plain and simple.
That is one factor that LED growers often overlook.
QUALITY LED lighting takes about 35 watts per square foot in flower (thats actual watts), if it's a blurple LED then you probably need more than that, like 40 - 50 depending on the quality of the light.
Know that overfeeding doesn't help, and most of the yield comes in the end when the flower is becoming denser so never chop early, wait it out.
Hope all that info helps you in your quest.