Why is my RH so high?

humidity does not rise. That is objectively wrong. RH is highest in lowest levels of a house and a cursory google search can verify further, if you want to. You still want exhaust up top for the heat, thought. Your tent will be some portion above the "lung room". Changing exhaust speeds will affect the resulting deviation from the lung room and inside the tent. If it's 10% higher, you need to drop the lung room down 10% below what you want the tent to be. The suggestion is that the CFM of exhaust can clear out the volume of air in your tent 2-3x. This is probably overkill, but still good to shoot for because your fan will never reach it's maximum CFM with ducting with a twist to avoid light leaks and possibly a carbon filter attached which reduces it 25% too. it's going to be 50% of that CFM in some situations. The 4" an should be enough for a 2x4 or 3x3, but you probably need it turned up to maximum. i use a 4" in and 4" out on my 4x4, but i don't use carbon filters, either. I run them at about 50% power. Foliage is what is the source of the RH... so, do what you can with your lung room and exhaust fan power... if that is not engouh, defoliate a bit - stages, see the impact, do more if needed. is it best for the plant growth? maybe not, but it may be better for the plant overall to avoid high RH. just depends on context. I'd only do it if it's still very high.. 40-60 i'd live with.