FWIW, various LLMs seem to think this is caused by nutrient imbalance, specifically potassium deficiency. That potassium deficiency can also be a knock-on effect from overdoing it on calcium or magnesium affecting potassium uptake. Finally, another thing to consider is pH testing the soil. If you're using a nutrient mix, you might need to flush the soil and start over (especially if you over did it). If you're not using a nutrient mix, you should consider doing that.