My initial thought just by looking at it is magnesium deficiency, although, we would need a lot more information in order to properly diagnose.
What strain is it?
How long has it been in veg?
What growing medium is it in?
Temperature in the environment?
Humidity in the environment?
PH of medium?
PPM of medium?
How often are you watering?
Type and strength of nutrients used?
Mexican Airlines, 2 weeks, Fox farm with coco coir, 80 temp, 60 hum, dont know the ph medium, don't know what ppm means and no pest. I water every two days base on the weight of the cup. For now fox farm nutrients
Hmm ok. It could be because your pH is out of range or it could just be hungry. Checking the PPM with a TDS tester will help give you an idea of how much nutrients are in the medium. Link to pH meter & TDS tester: https://amzn.to/3fCjV3A