Yeah its a combination of the following. These noobs have no idea. The main piece of evidence is the yellowing of the leaves from the bottom to the top. I'd say give them some nitrogen fert and cut away dead and yellow leaves. As for the plant on the right top it to keep it away from light.
The plants are two close to lights on top that whats causing the dead leaves on top of the right one. Also maybe lack of air flow going on?
There is also some kind of def. going on in your plants. To the best of my knowledge i would say lack of nitrogen, Have you been using any fert.?