Ok, I'm new here, but been growing outdoor and hydro for over 25 years.
I've seen way worse plants recover and give a nice crop.
If you think he massively overfertilised, rinse them out with loads and loads of ph adjusted water and then give them a feed at half strength then see how they look in a week to ten days.
If you think they haven't been overfertilised, just give them a really good watering and carry on as normal.
Gotta say, if that's your first grow, youre doing really well.
Hope that helps.