This is every growers nemesis. Open all your vents at the bottom of your tent. Also I've noticed you have your power bar along with other power supplies that you could move outside of the tent. Try it out and I guarantee you'll shed at least 1 deg. The only way to really reduce the temps considering you are already running an inline fan is to intrude AC to the tent. You can make a cooler packed with ice a homemade AC system but you need a fan to push that cold air in the tent there after so there is no easy solution my friend! We are all dealing with the same issues during the summer if you do not want to add with the additional power draw. Try moving your power bar and any other things that create heat outside the tent and you will see a difference, only issue it may become less convenient for you in the long run.