The things to focus on are simply, is the plant growing well? Does it look generally healthy, leaf shape/size, is it taking up water like it should etc.
I am only new to growing, but it does seem people over complicate, and worry and cause more problems trying to fix something that is fairly typical.
Dont stress about it unless things change drastically, and with soil, you have time and a buffer. They will not die, i can tell you that for sure.
When you do you water? It could have been a water droplet that caused the burn. Try checking the leaf chart for deficiencies, and match yours up. You will see that most deficiencies affect the plant in a more drastic way than yours, yours look 99.9% perfect and healthy..