I notice the growing tips lighten a bit in color to a pale lime green then a few days later there's the pistils or pollen sacks showing up at the nodes starting around the top.

maldo- the ferts I use and highly recommend are the fox farms line. Grow Big, Big Bloom, and Tiger Bloom. I use a combo of these and some of their other "enhancers"(really expensive but worth it). If you only get one of those go with the TB for flowering, it's 2-8-4 and you only need 2tsp per gallon of water(every other watering recommended) so the small bottle(about $20) will last you years basically.