That calyx is normal, it will get those on most of the bases of the stems, even throughout veg. So those are totally normal and not really a sure sign of flowering. Those calyx are actually a sign that the plant has reached full maturity. That means it's basically ready to flower but not that it is actually is. Just turn on an outside patio light or something and keep the plant under that at night and then slowly shorten the time the light is on until the days are longer. Thats what i have done to early flowering plants in the past.