sed8ed

Present room specs:
room size approx 8x8x24 feet sealed except for door (had to remove the airlock due to cooling issues
2 - 4x8 tables
1 - 2x4 table
3 - 600w digital (ballasts inside the room)
2 - 400w mag (ballasts outside the room, aircooled hoods)
2 - 1000w mag (ballasts outside the room)
780 cfm exhaust fan set up for room purge right now, was planning on recircing the room air through a carbon filter through this one
2 - 430 cfm exhaust fans (1 set up for room purge incase of overtemp, 1 pulling the exhaust from the ac out of the room)
1 - 12,000btu danby portable ac (dual hose) intake from the household cold air return, exhaust to the household heating ducts
1 - Danby dehumidifier
CO2 system
Harvest master room controller

All plants in soil until I perfect this system then going back to top feed recirc
Presently I am only running 2 of the 600w over the veging clones due to heat problems

I seem to have run into a problem with cooling the grow room lately, I can't seem to get the temps down below 85 with the lights on and 78 with the lights off... ambient outside night temps are around 75 but nothing seems to make a difference, even purging the room with both the 6 inch vortex and the 8 inch vortex. With the room sealed up, the lights and fans off but the ac on full can I achieve 78 deg at night.

*note* the reason all the lights are not air cooled is that I don't have enough available intake and exhaust ducting leading to and from the room

Anyone have any ideas on what could be going wrong? In theory, the ac should be more than adequate, unfortunately I can't feed the ac intake and exhaust outside due to this being in the basement (concrete walls, I was hoping these would work as a heatsink). I really need to get this fixed asap since the vegging clones desperately need to be repotted and then they won't fit in the one tray they are packed into, furthermore, i'm pretty well maxed on available power so another ac is out of the question