Without seeing the vehicle in person I doubt if a good guess can even be made . Isn’t your vehicle still in the warranty period ? You need to have this looked at before you have a real fire.
If you have access to a phone, you could post a picture.
Thanks Purebred. I re-edited this post and added the picture.
Are you speaking of the marks around the latch? My guess it is from what ever lubricant is used on the latching mechanism. Perhaps normal heat from the radiator is causing out gassing of the lubricant, just an idea, a guess, not a diagnosis.
If you are on good terms with the dealership, they MIGHT take a look at no charge.
The brown dots on each side of the hood striker pin are from road dirt the enters though the grill and the plastic panel below the hood.
Shew! What a relief Nevada_545! THANK YOU! I OWE YOU! Interestingly those photos you show me are of the same car I’m looking to buy that I posted the original photo of!! Thanks! 
My pictures are of a 2019 RX 350 so there is less dirt.
Are you saying that you don’t own this vehicle and are thinking of buying it ? If that is the case did you point this out to the dealer ? At least have them verify that is just dirt.