It's possible that there's an issue with the driver being used by your Mac.
Basically, you will need to remove the printer driver that's installed on your Mac then you'll have to add it in again. Follow the instructions below.
Click the Apple icon on your Menu Bar.
Select System Preferences.
Select Printers and Scanners.
Select your printer and then press the (-) button at the bottom of the list to remove it.
Select the (+) and click Add Printers and Scanners. (NOTE: Do not select the printer from the list of Nearby printers as this will often automatically use the AirPrint driver)
Select your printer (the one that shows Bonjour Multifunction under "Kind").
At the bottom of the window under Use: does it say AirPrint? If so, click the drop down and you should see a specific driver for the printer. Click Add.
Try printing an image again, and let me know the result.
Test printing out some prescriptions. You should now see it print quickly.