I'm starting to get this burns but what could it be. Any help please

Could be a calcium issue. Find a chart like this on Google to help you narrow down the deficiency or excess

Can you give us a little more info about your grow so we can properly diagnose? Indoor or outdoor grow? How old is the plant?

Are you in soil, coco coir, dwc? What size grow pot? What have you feed it for nutrients and when? Is that the only leaf impacted on the plant?