Your herbs are day length sensitive, and right now the days are still growing longer. They'll continue doing so until the summer solstice about June 21st. Once that day passes the plants sense that the days are shortening again, they hurry up and reproduce before season's end.
During the first half of the season, now, plants are working hard to put on as much leaf and stem as they can. The bigger the plant, the more growing tips will be able to support flowers. So that's why its responding so vigorously. Another factor could be a lot of nitrogen in the soil which is often the result of lawn water runoff that carries high nitrogen turf fertilizer with it.
Rejoice at the abundance, because once they shift after the solstice, the flower production is at the expense of foliage and your harvest will decline sharply!