Is this sun burn?

[Dunge]

My girls came from a basement fluorescent veg. four days ago.
I put them out in a visqueen wind block and cover.
It is an open tent so I can't see how it could have gotten too hot.
Will they 'hardened off' whatever that is?
It looks bad to me.
How bad is this likely to get?

 

[jagle]

funny my plants are starting to show something similiar, i think my issue is low humidity

 

[organicness]

Sun burn. Happened to a bunch of my garden seedlings that I was hardening off. Then we got 9 days of rain. Can't win over here. But definitely sun burn.

 

[Seamaiden]

Definitely sunburn, and yes, they'll grow out of it. The affected leaves can't repair, but the plant will go on to grow new ones.

 

[jagle]

what would be causing that indoors?

 

[Seamaiden]

Have you changed lights recently? Especially going from a very old HID to a new one. This occurs in corals when people add or change out from very old lights to new lights.