Hey Bertabud, you're right to look for milky trychomes that's the only way to tell ! just a reminder you want to get a magnifier at least 40x and preferably 60x for comfort in order to see them. That's really the only way to tell, another good way to tell is simply to add 2 weeks to the recommended time from the breeder. So if the breeder says 10 weeks, then it will be 12 for sure ! Finally what i can say is that harvest for dark devil auto usually take 10 to 13 weeks, so you'll be ready in 3 to 5 weeks - basically last month ! That means wait another week at least before flushing. The yellowing is totally natural, but the burnt tips are a sign of nute excess, so cut the nutrients by half and respect the water - water - feed - water - water - feed schedule. You're almost there my friend, good luck ! 🚀