Too high FG problem

Im using an HERMS 25Liter brewing system I have built myself. And i think ever since switching
To this system i ended up with beers with high final gravity.
I usually end up with 1.020 after the fermentation.
A porter or brown ale i think that kind of FG gives it the right body but with
Pale ales and lighter beers its no good.

I usually mash at 65 celcius(149F) circulating tha vort through the stainlesssteel coil in the hot water tank with is set to 65 C degrees. Usually do a mash out after 60 min on 65c to 78C. A total mash length of 90 minutes.

I usually use one smackpack wyest to 17 liter i fermenter. This last brewday i used 1 whitelab tube and an older wl tube i made a starter on end stept it up a few times with new "yestfood" dme so i had more than enough yestcells for 17 liters.

I also did lower my mash temperature on this brew to 64C , still the FG was 1.020 after over one week in fermenter.

Any idea how to change my rutine so i can fall all the way to 1.010 something

Cheers