Welcome to the forums hope you enjoy our community and thank you for your first post. 🙂
When boosters are working correctly the connection light (the two arrows) will be off and the connection light will be on. What lights are showing on your boosters? Is the range better since you have had them? I would suggest looking on this link for info on our Boosters.
I cannot find anything in regards to a guest network so I am inclined to say no they won't boost the guest network you have set up.
Please let us know how you get on with is and we will be happy to help you further if you need it.