dude your plant is almost ready, but the only way to really know is to get a 40x minimum magnifier, 60x is comfortable 100x+ is overkill but awesome and look at the trychome development to see if they are cloudy or amber or clear, you should be able to tell right away ! You're aiming for all cloudy no clears, some ambers. So yeah i would say go with your intuition not the grow shop guy and keep watering with plain water until you're done, not long left ! 🚀