cold A/C air VS fresh/hot intake air

So like every summer heat is an issue. And this one is getting hot! I have two a/c units in my room which are capable of cooling it down when my intake is not blowing hot 90+ degree in the room. Lights are on at night and with the cold intake air temps are fine (75-80). But when lights go off during the day the temps sky rocket (100+). Due to the intake constantly blowing hot air into the room. So, my question is should I cut the fresh/hot intake air off during the night cycle (day time) to keep the temps reasonable? And keep the exhaust on or off? Considering the two a/c units have an exhaust of their own.. Or will I be suffocating the plants? Do they need constant fresh air during the night cycle? If so which is worse less fresh air at night cycle or very high temps?

My opinion is that you don't need fresh air when lights are off because plants don't photosynthe when lights are off, you could also get away with sealing your room when lights are on if you have some form of co2 in the room. My room is sealed with one ac, lights ran at nights cause its been in the 90's here lately and co2 burne,r but without some source of co2 your plants will die from lack of oxygen