Air Conditioning - a/c not cooling very well

i have a goodman 2 ton central air unit and it has just started to not cool very well, the system is around 15 years old. i just had a tech out here yesturday and the freon level is good. the compressor seems to be working fine, the big pipe is cold and wet. the air filter is clean. i measured the temperature, 75 degrees at the filter and 64 degrees coming out the vents. someone told me to check/clean the A coil, so im fixing to do that. is there anything else i can check or do? thanks.

clean the blower

the blower in the inside unit?? i have before, but it was very difficult to clean, cause its got a cage around it and you cant really get down in it. but ill clean it again.

well my unit seems to be doing better, i cleaned the coil and the blower motor, but what i think helped the most was the insulation inside the unit was getting sucked in by the blower motor not letting much air by, so i took a peice of sheetmetal and screwed it to the unit, i think that helped the most. thanks guys