could be borers - i experienced them this year - a grub that will eat its way up the center of the stalk and the plant will snap or bend over at this area - i successfully staked and taped the break with paper tape and plants are growing -the buds are a little smaller then plants not atatcked but they are doing well- pot plants I have found to be very resilient and can still take in nutes and water with a lot of the stalk damaged