Transpiration is the other big one, all three work together, photosynthesis traps light which triggers transpiration where water leaves the plant as gas, as one molecule of water transpires to the environment another enters through respiration.
I know these plants have already yellowed but what you're seeing is a transpiration issue caused by a lack of respiration at the roots. Same as humidity and temps, when they go out of balance, the plant loses more water than it can take in. Then stomata close to limit water loss and once they close photosynthesis can't take place.
What you're seeing when you shut the lights down is closed stomata, stomata close under low light and at night, same same as above. This is why you're not supposed to water at night, water a couple of hours before lights out, etc etc. With stomata closed they can't get rid of water.
Personally I reckon they do well either way, when things are dialled in they don't shutdown at all, I like to give mine a night cycle though.