I have a little problem. My plants seem to be growing very slowly

A customer has a question and I hope we can get some opinions on it, thanks.!

I have a little problem. My plants seem to be growing very slowly. They are about a month and a half old and are only about 6 inches, and the others are about 41/2 inches tall. They also have yellow on the tips throughout the whole plant. I am using a 1000 watt LED light with all the spectrums. I recently moved it as high as the light will go, about two feet, from about a foot and a half. I am also using the defoliation method, which seems to make the plants very thick. Is there any way to speed or force them to grow higher? I am using Tutankhamen seeds which are very powerful, but every seed I seem to plant seems to be growing very slowly. Is it the light? I have three plants, two in 12 inch containers and one in an eight inch container in a closet that is 2’x3’. I can’t figure it out. Also, it seems that my plants never seem to finish. They get close but I never get amber trichomes or get that nice smell they are suppose to have. I had blueberry plants that were good, but not great, and didn’t have that blueberry smell. Should I stop fertilizing completely two weeks before? I appreciate your help.
Vinny A

Dont you have this posted elsewhere? Thought @bob31 @Countryboyjvd1971 already advised on this. Multiple posts wont help. If not my apologies


Good catch @Laurap

This is being resolved here:

Why are my marijuana plants growing so slowly - #2 by Countryboyjvd1971