[Unity2D] Make fire spread through tiles in Platformer

Hi I'm pretty new to Unity,

I wanted to make a system where fire would spread from one tile to the next ( e.g. Nuclear Blaze).

I didn't know how to do it with a Tilemap, so what I've done is to create gameObjects as tiles and use OnCollisionStay2D to detect other gameObjects next to them, and "set them o fire" if they are not already.

This is what I have so far:

It is working, but I'm afraid this might cause performance issues in the long run, specially for entire levels. I don't think having so many OnCollisionStay2D and RigidBodies is good, performance wise. But again I'm a begginer so I don't know, and I can't think of any other way to make this work.

Any suggestions?

Thank you. PD: Also, any tips on how to create procedurale fire (tutorials...)?