wild temperature flux

I'm running 2 600w hps with 6in vented hoods in a 4x4 tent. I've got the hoods ducted together with a 424 cfm fan blowing into the first hood and a 8in 747 cfm (with 6in reducers on either end) sucking the hot air out of the line and bliwing out the tent. Now my outside room temp stays between 61 and 68 with no problems. However with both lights on my remp will go all over the place averaging in the low to mid 80s. With one light on it doesnt flux around it just stays in the mid 70s with no issues.

I'm not sure why I can't get and keep temp consistent for one or in the 70s for another. I sat inside when it was all sealed and I can feel a strong cool breeze blasting from my vents.

Any suggestions would be greatly appreciated.

Sounds like a lotta heat for a small space.
Keep in mind every time your ducting bends your cfms are significantly reduced.

Also your temp readings are probably off it's real hard to get a good reading with all that concentrated heating.

I would get the ducting to pull the heat from the lights with one fan. Works best if it pulls from the top cause heat rises.
Get your second one to bring in air from the outside and pour it over your plants.
Maybe get another fan inside the grow room to circulate it.
Finally take temp readings everywhere around your plants to get a better idea of the actual temp.