at a guess if they all are and this is a guess id pull them out and despose of them and start again.i would i guess wate for someone more reliable on here or maybe ask a specific persen like moon grower or bamboo or drbob maybe . i hope ive helped take care bye for now .

Where are they growing - in the ground, in pots, in shade or sun? And how long have you had them?

COULD IT BE POSSIBLE THAT A ANIMAL HAS WEED ON IT, OR SOMTHING SPILT ON THEM, THEY ARE PRETTY HARDY PLANTS SOUNDS LIKE SOMTHING HAS SOAKED THEM,,,,