Definitely nute burn but they also look overwatered. Your mix looks like doo doo; sorry can't think of any other words to describe it; so trying to be positive lol.. think you need improve drainage of your mix and to do a good flush to get rid of the salt buildup in your containers. Let the soil dry out a bit & then pop them out of the containers. See if you can loosen the root ball & then rinse it off in a sink, tub, or outside with a hose.
Before you do this get some decent soil & add some extra perlite & maybe even some coco coir. Place in a vessel on standby....then once you've flushed the roots gently by hand replant into your fresh well draining mix. Give no nutes for a week or so & then if you want give them sparingly and at half strength or less. Only trouble is this could affect your harvest time; if these were my plants I would increase hours of light to let them veg for couple weeks to allow them to recover. You could end up with stringy delayed flowers and diminished yield if you let them go as is. These are not even showing pistils yet; you can easily flip em back again.
It does not matter much to the plant if you switch to bloom formula when you flip the lights. IMO it's better to keep giving veg nutes for the first 2 weeks of flowering transition and then giving bloom nutes in the 3rd week when they actually need the extra P.
