YES . During the dark cycle they must remain in total darkness for the complete 12 hours. that will diffently slow um up. only other thing i can think of . Is they might be root bound. how much dirt is each plant in? should be 5 gallons per plant for great result.You can also just go with the lowryder plant. Grows in 1 1/2 gallon bucket and is fininshed in 8 weeks . they are auto flowering so they bub from the beginning till the end no matter what the light cycle is