I feel there was something wrong with the roots ( some type of rot, or a big hit of salts), it looks like another has or had an over fert problem too. overall not looking too happy like they are not getting oxygen at the roots.
Don't worry you will get quite a few buds outta there
I had a few guerilla plants in different locations do similar once, they died very quickly and after some investigation, it was over fertilisation at the very beginning when I prepared the holes, I had a small handful of urea in the bottom of the holes thinking it would break down before the roots got there. The plants grew fast and soon found the little patch of death I had left for them. Each plant just a week apart died within days.
It's just cool what you can do with a few bulbs, especially now there is the led type that is quite an amount more efficient than the CFL type.
Rock on man, Happy Days.