I've only had a couple foxtail on me, and I can tell you it's most certainly attributed to genetics!!! I've grown 3 strains simultaneously with the same nute mix and pH, same light, same environment; one one of them foxtailed.. Regardless, think of it as extra bud, since that's really all it is!! I trimmed mine close, and saved those protrusions for my shake/trim blunts.. They have the flavor and the potency, so why not, right?? 
