Classic potassium deficiency... These ladies are in flower now and no longer need only grow nutes... you need to start your bloom nutes, like now... I would also worry at this point, since you've been giving them only grow nutes, that you've created a nitrogen toxicity which will lockout other nutes such as calcium... so flush your plant - 3x the pot volume of pH'd water but into that last bit of water, add some bloom nutes only... then let her dry out. When you resume watering/feeding, if you feel you MUST give her grow nutes, only give about 1/4 strength and really pump the bloom nutes. A PK booster would also be very good to add in...
Good luck