Probably, it depends how many sites you have in your network. We count each site on your network as a standalone site so you’ll need to purchase a Speed Fix service for each site you want fixed. Some of the changes we make as part of our speed optimizations will have an impact on your entire network (a positive impact).
If you have a question about your multisite environment, shoot us an email at questions@www.wpspeedfix.com and we can discuss in more detail.