Thank you David for your reply. I have tried putting leakage paths in different places, I tried adding exhaust fans to each zone. I still need to try pressure drop components (I did try it earlier, but maybe in the wrong place). I was reading online, and apparently some people who faced this problem solved it by changing their window configurations and openings (AFN windows), but I didnt get the logic so I tried it in a dummy way and didnt work either!