Without knowing a bit more my best guess is it looks like nute burn from flowering nutes when it needed some veg nutes still. Also if you're growing in soil it could be that your soil's PH is out of whack. When Leaves start looking like that the soil's PH is usually really high like 8.0 or so. What I've done is flush the plant with 6.0 PH'd water to get the soil back down to about 7.0. Then water normally with about 6.0-6.5 PH'd water with half it's dose of veg nutes and just a bit of bloom. (Assuming this is in flowering.)
How far away is your light? Light type?