Grow Room Ventilation Help

Ok so I have a closet grow set up, and I have the closet sealed with 4mil plastic. I have a 4in inline fan pulling air inward through the plastic sheet and a 6in inline fan pulling air out through a carbon scrubber and out of the plastic sheet via ducting that i purchased. However, the 6in fan is pulling air through a 6in to 4in reducer and into a 4in sized duct which then is connected to the plastic sheet. Also the setup has 2 fans moving air, one small fan blowing directly on the plant and one fan blowing upward and past it. So heres my dilema. Despite what I thought was good air circulation, I still struggle to keep the temperatures where I'd like (75-85 degrees) Sometimes it drifts up to 88-92 so I was wondering if anyone had any suggestions on how to keep it better leveled aside from purchasing a mini ac unit?

The only way to maintain lower temps is to remove heat from the room. You say you have fresh air intake/exhaust covered and are still experiencing too high of temps so your choice is to either air-cool/water-cool your light, or purchase an A/C unit of some type.

Hey, small spaces require air cooled hoods or tubes IMO. Keeping that heat from the light outta ur grow by running the filter to the hood then to exhaust fan will by much better for heat control.

Alright well that sounds like the solution then. Ill look into getting a hood w/ air/water cooling capabilities
Thanks guys