Is this light burn?

It is not stress, light burn or a deficiency/disease, just a mild leaf mutation that is quite common in cannabis. She will be fine and will not need any "rescuing", her next leaves should be perfectly normal. This condition is known a "variegation" and some plants can have many leaves like this throughout their life or sometimes only an odd one here and there, but most plants will have none or only a very few. You have nothing to worry about, your plant will be fine and is not suffering from anything. Hope this helps, Organoman.