It looks like you live in Florida right? I would guess its a corrosion problem of some sort due to the salt in your region. I could be wrong! Check this out from the Lexus web site.
Corrosion Perforation Warranty
This warranty covers repair or replacement of any original body panel that develops perforation from corrosion (rust-through), subject to the exceptions listed in the Basic Warranty page. The Corrosion Perforation Warranty coverage is for 72 months, regardless of mileage.
Just found this for you to Basic warranty covers everthing except:
*Airborne chemicals, tree sap, road debris (including stone chips), rail dust, salt, hail, floods, windstorms, lightning and other environmental conditions.
Some Lexus dealers are difficult to deal with when it comes to this issue. Notice the part 72 months reguardless of mileage!!!!!!
Let me know if this helps.
Toby Rivers
Lexus of Shreveport
800-335-3987