What are your conditions? What are you growing in? Lights, medium, nutes, water pH, etc? Are these in veg or flower? How far along? It's hard to offer advice without more input from you. There is a troubleshooting form. Perhaps fill it out?

At first blush I'm going to guess a calcium deficiency and a bit of P needed too. Up your nutrient dose a few ml / gallon and add some unsulphured molasses @ 3/4 to 1 tsp / gallon. Good luck!