It bolted. There seems to be conflicting reasons for bolting of brassica:
1- warm weather. (how warm is warm ?)

2- long hours of daylight.

Here where I garden, the night temperatures were around 45F and day highs about 57f. But my Bok Choys are bolting. Varum???

so I suspect the latitude or long days. I plnted them as early as possible and they grew slowly and now bolting while they are small.

some say fall planting is better. But I have seen Chinese cabbage bolting in the fall too. I guess there must be a secret that we don't know(me and you, OP)

WHAT YOU CAN DO NOW? I think just harvest and stir fry them , what else can you do ? lol