looks like your barley getting trichomes (the tiny crystals that produce thc)..looks like you have 3 or 4 weeks to go..wait for the trichomes to grow they will mushroom out at the tops and eventually turn milky white and then amber that is the time to harvest plus your buds will get bigger and more plump..be patient and you will be happy
also if you know the time you started flowering that will help..its going to take at least 8-12 weeks of flowering for them to be done depending on the strain.