Yokohama/ warranty experience ?

Hello all, I got a set of the Yokohama Geolandar G015 (replacement for the at/s) back in September. I’ve only out 8000 miles on them, but they’re down to 7/32! New is 13/32. Somehow I’ve used half the tread of a 60,000 mile tire in 8000 miles? Anybody have experience with Yokohama warranty honoring or their customer service? Do I really have to wait until they reach 2/32 before the manufacturer will do anything? Seems like these are very obviously faulty tires. Funny thing is, all 5 of them are wearing at the exact, accelerated rate, and I got the spare from a completely different vendor. So it seems like a production problem, one that Yokohama should be aware of...