What did you wash plants with?
Looks like nute burn.
Just water
My first thoughts Looking at the pictures the flash did not cause this problem I would start by checking my PPM runoff. As mentioned looks like nute burn.
Did you wash plant down under lights and leave them on for an hour or more? That would do it.
Thank you
Yes wash plant down under lights
How l can treat
Very good point @Myfriendis410 That’s why they pay you the big bucks. 
Nothing you can do: the light burned the leaves due to ‘lensing’ and will not recover. If spraying plant it’s best to do just before lights out and put a big fan on it. I’m not a big fan of foliar anything except to control pests or fungus.
Plant will survive and it’s a ‘live and learn’ moment.
Thank you
300x150x200 cm tent 23 plant
Light 4x600 w 2x400 w
For size this tent this light enough or not ?
