I generally add two weeks or so to the grower’s recommended time. If they stay healthy, they generally should go longer than 70 days (more like 90-100). I haven’t grown Gorilla Cookies so can’t comment from experience, though I have an 11 day sprout of that variety now. I have seen some massive buds from this line, so I’m pretty certain it’s not genetics in your case.
Normally, 75% brown pistils is still pretty far too early for harvest. Don’t believe much of what you read online. Most here will recommend 100% brown and then beginning to recede. Your plants aren’t ready for harvest. But they also don’t look too healthy.
There are too many unknowns to really comment much (what is your grow medium, for example?). The plants looks pretty significantly over pruned. Where are the fan leaves? Autos are small enough that I do very little pruning on mine - doesn’t take much to improve light penetration on a three foot plant. You may have stunted growth by over-pruning? Just a guess, but bud growth does look stunted, and you may need to harvest early based on health of plant.
You’ll get some smokable herb from there and improve on the next run. Less is more with autos. Try a more hands off approach? Don’t know, and trying to be helpful, not critical. Enjoy the harvest.
PS: also, next time out try some low stress training. You can dramatically increase harvest. Less pruning, more training.
