Welcome to Club Lexus.
When you have a "check engine light" (CEL) indication, I believe three lights appear, including the two you mentioned. The chances are that you have a CEL event. You need to borrow a CEL code reader (AutoZone) or purchase one (Costco) and give us the code(s), if any. For me, it has always been an airflow or Oxygen sensor that caused a CEL event. This is not uncommon on all newer cars, not only the RX300.