you need negative air pressure (pasive income hole covered eg. with a cardboard box against the light) - pulling out with both fans in a row if necessary.
i once had the same problem - and found it much better to put ona gel or other room ambients
on a rag inside a bigger plastic bag with lots of little holes.
Then you tape, wire, fix that bag onto your outcoming air tube and blow it up - the air mix is much better inside the bag
If the air coming out of your plastic bag still smells to weed - you have to renew the carbon filter.