If your fans have any model info on them you can google it and find the specs. That way you will know when you buy a new one if it is in fact better than the ones you have.
I am unsure if taping them helps much with more airflow, but I think it helps the pressure be higher, which is what you need to effectively push air through that restrictive carbon filter.
Please be cautious if you decide to add intake fans. Myself, and many others, have found that any fan except exhaust swirls the air and doesn't give the exhaust fan a chance to get rid of the hot air.
Just some tips for y'all. The plants are looking great!