Hi
I agree with all the posts in this thread. Please concentrate on a good and healthy hay based diet.
It is a good diet that will allow your piggies realise the optimum of their genetic inheritance and can ultimately add 1-2 years to their life that they won't have on less good diet. Keep in mind that a carefully balanced veg diet, 1 tablespoon of pellets per day and unlimited hay only replace the ca. 20% of the diet that used to be covered by supplementary forage - any treats also have to come out of the same limited category. Over three quarters of what piggies eat in a day needs to be hay. High sugar veg and fruit, high calorie pellets and any treats are ultimately life shortening.
Here is our diet guide:
Long Term Balanced General And Special Needs Guinea Pig Diets
The good news is that it doesn't matter whether a piggy is large or small in terms of having a good chance for a long life. I have had several piggies that you would class as 'too small' live to celebrate their 8th birthday nevertheless. In fact, I have had more 'small' piggies live beyond the average life expectancy than large ones.
Please take the time to read our weight management guide and learn about the importance of checking the BMI to ensure that your piggies are at all times the right weight for their individual size when you monitor their weight weekly during their whole life on your normal kitchen scales. Weighing is your best ally to help spot developing problems early on and to support your piggies during illness at the correct level.
Here are the links:
How To Pick Up And Weigh Your Guinea Pigs Safely (videos)
Weight - Monitoring and Management
Please also keep in mind that guinea pigs won't reach adulthood until around 15 months, so please do not panic.
Your little one has still got several months to reach their own genetically determined weight and adult size. Right now they have not long started teenage!
But they are now coming up to the age whether an overabundance of pellets will move from going into their stop and go growth pattern that is characteristic for teenage and where too rich/much food will instead increasingly contribute to the growth of yellow fat around the inner organs, which is life shortening and also a major operation risk factor.
We have a chapter in the weight guide that explains how weight in guinea pigs develops over the course of a life time, which you may find interesting.