There are no age to weight guides given birth weight varies widely and then all piggies get to their natural genetic adult weight in time and given there is also a wide variation in adult weight, you can only go by what is healthy for the individual piggy by checking their heft.
One tablespoon of pellets per pig per day is enough. So if you’re giving two tablespoons per pig, then you are giving too much.
It can also depend what pellets you are feeding though. If they are on specific young piggy pellets, then they definitely only need one tablespoon per pig per day as nutrients are already adjusted. They can have young piggy pellets until four months old. They contain alfalfa which is too high in calcium and can lead to bladder problems if fed for too long. They do not need young piggy pellets nor alfalfa though so don’t worry if you aren’t giving them.
If they are fed normal adult pellets, then they can have two tablespoons per pig per day until they are four months old (then it must drop to one tablespoon per pig per day). However, they are also absolutely fine to be fed a normal adult diet of one tablespoon per day. If they are loving their pellets and at risk of eating too many of them and then not eating enough hay, then don’t give them more than one tablespoon.
Pellets are more like an unhealthy dessert. They will put weight on with eating them, but it’s not healthy weight gain. Pellets (including adult pellets) contain a lot of calcium (along with unfiltered drinking water) which can lead to bladder problems. This is also why it is recommended to keep pellets strictly limited and water filtered.
They will gain weight in their own time with a good diet of unlimited hay, 50g of veg and one tablespoon of pellets and it will be done the healthy way!
Weight - Monitoring and Management
Long Term Balanced General And Special Needs Guinea Pig Diets
