What is the streak on my fan leaves?

Noticed it about a week ago, should I be alarmed? Indoor grow watering whenever the soil gets dry by using a Soil tester, under a Mars 600 light and a VS1000 in a 4x4 Medium is soil, I’ve done 1 feeding of fox farms grow big at 1/4th of the recommended usage, soil PH is around 7.5

Do you possibly have a photograph of the entire plant?