I had this happen to 2 autoflowers. I had a defective COB LED that was glowing for 2 hours after power goes out. i thought that was the cause... but could have been genetics. anyway, if not doing 24hour light, check for a leak. if so, maybe my suspicions are correct, but i thnk it's more likely genetics.
"dr. ginspoon" grows like this and at one time was one of the highest potency buds you could get. you can easily find an example on google image.
my experience.. the autos that looked like this tasted like total shit... small sample size, so don't do anything based on that anecdotal nonsense. one of the reasons i stopped doing autoflowers.