I've managed to get 3 Atlantic Giants germinated this year. One's doing fine. The second one got a small bit of damage to the stem when I planted it out. It seemed to thrive, even though the damage on the stem got worse (stem got really thin, then went dry and shrivelled up where the damage was). Then it died. Now the stem on my third one seems to be shrivelling and drying - even though this hasn't been damaged. Despite this there are flower buds appearing and the leaves look very sprightly. It's in a raised bed on my allotment. What's going on?