Hi!
The weights are on the smaller side but that is not a worry. Important is your normal daily care. Keep in mind that your babies won't reach adulthood until they are around 15 months of age. That gives them plenty of time to realise their individual genetically determined optimum. Guinea pigs have a very large range of perfectly normal sizes/weights. The important bit is not whether they are 'average' but whether they are a good weight for their own size (BMI or 'heft') and not overweight or underweight.
At this young age, as long as your babies are active, eating and playing, they are doing fine.
Never be tempted to think that stuffing your babies with empty filler calories will make them grow faster or bigger - they will simply come out of their initial fast growing phase sooner and will then start building up life-shortening fat layers. Rather concentrate on a healthy grass/hay based diet to make them as fit and healthy as you can so they can hopefully enjoy a long and healthy life. The correct diet and being careful with fattening high sugar foods can add 1-2 years to a life and take your piggies from the lower end of the average life span to the upper end or beyond. It is never the quantity but the quality of what you feed that is making all the difference. The problem with 'average weights' is that they include at the best 50% of all piggies but that also means that the other mostly perfectly healthy 50% are considered to be 'wrong' in some way or other because of an entirely arbitrary human attitude to weight (which is frankly not the healthiest one).
My Morwenna ('White Seas' in Welsh) was only 40g when born (which is about as low as it gets) and needed feeding support to make it through the first dodgy days. She always remained on the dainty side but she has just celebrated her 7th birthday and is set to become the longest lived of the three siblings despite having had the worst start and staying at the bottom end of the average weight range. My sisters Heulwen 'Sunshine' and Hedydd 'Skylark' even lived to celebrate their 8th birthday despite both being small all their life long.
Happy 7th wheekday, Mererid and Morwenna!
You may find these information guide links here very helpful. The weight guide teaches you how you can work out whether your piggies are a good weight for their size at any time of life ('heft' or BMI), how weight changes over the course of a life time and what you are looking out for during the life-long weekly weigh-in and body check. We cannot explain it all in every post for everybody but you will find lots of really helpful in-depth information as well as practical tips in our guides.
Weight - Monitoring and Management (all about weight and weighing)
Guinea pig body quirks - What is normal and what not? (teaches how to learn what is normal and not)
Long Term Balanced General And Special Needs Guinea Pig Diets (diet is key to long term health and can help to promote a longer life span.