it could be from stress it could be genetic. The plant looks healthy otherwise and it looks to be early in flower which is bad news. If you can afford to kill the plant now you might do this to prevent pollination of other plants. If it's your only plant or a big portion of your grow then pluck any male sacks as they appear. The one in the picture is early enough that it hasn't shed pollen. Remove it carefully and water will kill pollen so you can spray your plants often (not too much to cause mold or water spots).