I have a 2000 SE. My old company car. Came with Firestone Affinity. The affinity tires seemed OK but wore out at about 25k.Worked great till I rotated them. Company would only rotate every 10k and would not allow alignments, as cars were turned over every 36mos/36,000. At 25k, Firestone put on a set of FT70C'*. They wore uneven due to no alignment.
When I bought the car I had a set of V rated Firestones put on. I could not get those tires balanced period. First had two alignments, balances, etc.
Took them from the Firestone dealer to another dealer. Paid $125 to force road balance. No luck. Finally, had the tires taken off and put on Bridgestone Turanza el200? These are T rated tires. Force road balanced. The car is about 95% back to where it used to be. Very nice tires.
2nd dealer, who has extensive experience with Lexus and high end cars was convinced that the tires were IMPROPERLY STORED!! He told me that if tires are stored on their side vs. being vertical, it definitely effects the belts. He also told me that he thought the rubber compound may have been too stiff for my suspension.
Now maybe everyone thinks he'* crazy, but he called Firestone and spoke with them re: his findings. Firestone reimbursed me for the new Bridgestones, mounting, balancing alignment and road hazard warranty. My tires were a year old, and I was trying to remedy this since they were new. They were great.
Sounds like you are having the same problem as I was, and another poster may have hit it on the head re: the belts. Firestone picked up my old set of tires and I know they were sent for examination. But they told the 2nd dealer that their findings are for future use and they would not discuss nor reveal what they found, if anything.
Being you got these mail order, I would call and insist on another set not from the same group. The dot or small circle referred to by another poster, in my case it is yellow/gold, does in fact line up with the stem.