Sounds a good weight to me, what's important now is to monitor any weight loss.
Most of the well-known and reputable websites that provide cavy care information make the claim that guinea pigs hide symptoms or signs of illness or disease. Being prey animals, any illness that makes them weaker makes them more vulnerable to predators so one could make the assumption that the statement is correct.
See some of the websites below..
"It is extremely important to be very aware of your guinea pigs' weight, behaviour and overall condition. Guinea pigs will hide early signs of an illness until it has progressed quite far. Unfortunately by the time obvious symptoms are noticed it can often be too late to help them. This is why it is so critical that guinea pigs see a cavy savvy vet at the very first sign of illness or discomfort."
Source:
http://www.guineapigsrusrescue.com/illness.html
"Cavies can hide symptoms in the early stages of an illness, so once the symptoms become apparent, they may have been ill for one or two weeks."
Source:
http://www.guinealynx.info/healthycavy_orig.html
"Like any other living, breathing being, I can get ill. But unlike predators, I hide my illness and weakness in order to survive. It is your responsibility to keep track of my weight and to notice when I am cold and when I am overheated. Know my body and the feel of my fur. Know my eyes' brightness and my ears' sensitivity. Notice when my health is failing me. For my sake, know me."
Source:
http://www.guinealynx.info/plea.html
"Guinea pigs try to hide signs of illness, so by the time you notice something is wrong the illness is usually well-advanced."
Source:
http://www.cavyhaven.org/care.html
