Agastachw blackadder changed colour

Does anyone know why my agastache black added would have changed colour.

Bought them last year and they were definetly blue with hints of dark purple maybe.

This year 1 was lost over winter, the other 2 have come back with more stems, they are not as tall and they are a definite mauve - purple (more the colour of verbena, no hint of blue). The flower worles are also much further apart, so the effect is a less bushy flower.

Any ideas???