If you never had this problem before, and you haven't changed their feed and you have billies on the holding (even not in close contact) I would certainly think your goaty milk (at this time of the year!) is connected to the girls coming into season... I would be careful to introduce any significant mineral doses if you have not needed them before, and discuss with your vet if the problem persists. There was a good discussion thread on this problem a while back on the BGS forum, I cannot remember all of it, the jist is though that you need to test the milk from individual goats and make sure to keep goaty milk separately - it is still perfectly ok for other livestock or kids (of the caprine variety). It may be just one of your milkers who has that problem, and mixing the milk from several spoils all of it.
My GG's have been in season, although not obviously so, only had a significant and very rapid drop in milk yield, which has recovered since. No goaty taste though, I have no male on the holding.