Trouble keeping the new mylar tent cool

My original tent was much smaller maybe 3 x 3 x 5, all I needed was an intake and dual outtakes on either side of the tent. This worked fine for my small 250 watt air cooled digital MH light. As the temp stayed around 77 consistently all day until night when it would drop to about 69.

However, I recently installed a 4 x 4 x 7 tent while brutalizing x1 400 watt cool-tube MH in addition to a x1 600 watt cool-tube HPS, I have both connected to ducting and separate intake in addition to outtake fans and honestly the lights themselves are staying relatively cooler than my smaller 250 watt air cooled hood ever did, my problem I think lies with my intake, which is a insulated 6 inch ducting attached to 2 6 inch inline fans. Maybe this summer is just hotter? Anyways my question is how can I drop the temp from about 83 degrees to something more like 70-75 without spending hundreds of dollars on an AC unit? I'd say my budget is 200

around 81-83