Weird substance turns to burn

No nutes , 75 degress , 7 ph , 1 55w 6500k CFL bulb , 1 week since popped from dirt

One day I noticed this substance on one of my leaves , didnt think much of it

A few days later it turns to a burn



Can someone please tell me whats your thoughts on this

12 views ? , anyone wanna help me out ..

it doesnt look like the end of the world

it could be a water spot or anything