Basically, solvents or extreme heat will reveal whats already there unseen to the eye. If the tank is 15yrs old, these marks most likely were right on/under the surface from the side panel bowing for all that time under load. Again, i personally would not be overly worried. Its pretty much just cosmetic.U might be right with the
Crazy I was smelling nail polish other day , I ask my son 4 years old did u do this he said no , I said u sure he said I sprayed something So u right tht could have done it
WOW