Very Slow Null Printer/Printing

We're running our Tessitura clients in both Citrix and RemoteApp for all three environments, PROD, TEST, and LAB. The null printers are installed on both the RemoteApp and Citrix servers and are shared across all three environments. 

Strangely, only PROD is running really slowly when printing to the null printer, taking up to a full minute to (not)print just a handful of tickets. TEST and LAB are fine. Any thoughts on where I should look to resolve this?

 

Thanks, MJ