Dude you need a tad more info to get a accurate response. Just a single pic aint gonna cut it. Give as many details as you can. To start where on the plant did this get taken from down low or upper canopy? Do any of the other plants show this condition? . Type of lighting, distance to canopy, feed regimen ie: ppms Any sign of pests? Have you even looked for pests to id any critters. Do you foliar feed with lights on? the list goes on