Negative air pressure

I have recently flipped to flower giving my two ladys 36 hours of darkness and switching to a 12-12 cycle.

however when the lights are off i need to close all flaps on the 2.3-2.3 mars hydro tent to ensure there are no light leaks.

But with the two 4" fans on and my carbon filter also on( Filter on inside and fan on the outside) i am experiencing negative air pressure ( the sides of the tent are bowing in! )

I have run some more 4" ducting from a seperate hole and meshed it so airflow is not as extream and to get outside air into the tent but the sides of the tent still bow in.

So my question is simply,

does negative air pressure effect the plants or do i have nothing to worry about

Thanks guys

Kind regards

LG

H