was going to suggest over water as well.... maybe you can take closer pics of each of the plants?? Its kinda hard to see anything detailed with that pic.
What kind of soil are you using? How hot is the cab? Your plants root system might not be developed well yet, try finding an additive like rhizotonic to help with this.
Don't see a lick of perlite or anything in that soil. What kind of soil is it? How's your temps and airflow? How much light is that too? A pic in normal light would be good too.