Hi and welcome!
Take a deep breath and calm down! As your piggies have still had access to fresh hay on a daily basis, they haven't actually suffered much - your diet may not have been ideal, but it was not wrong wrong. It's piggies reared on breakfast cereals, leftover pizza or curry or suffering from long time neglect where the damage can often not be undone!
Just continue with a good diet of unlimited hay, some balanced veg and a few pellets and give them a good piggy life.
Have a look through these guides here; you may find them interesting and helpful. We have got lots more information at the top of our various Care sections, but you are always welcome to ask any questions you may have in a friendly way.
New Owners' " How To" Starter Kit
Most of my adopted rescue piggies come from less than ideal to downright horrible places, yet most of them live a normal life span with good care. But I have lost some from apparently not so bad backgrounds at a younger age to illness. Some of the old pensioner piggies that I have adopted aged 4 or 5 years old have lived longer with me than a couple of youngsters. You just never know!
I've grown up with guinea pigs at a time that we now consider the stone age when so little was known about good home care or medical care in vets - and yet, one of my childhood piggies lived to the glorious age of nearly 10 years old and they still have lived happy lives. None of my adult piggies has ever lived as long as that yet, but at least I know that they have all had the best and happiest of lives that I could give them with the knowledge at the time.
We can never control when or what our piggies die from the same as you can't do it in humans. Illness, genetic time bombs, heart attacks and strokes out of the blue happen. Concentrate on making your piggies happy and bless every day they are in your life and make you smile; don't concentrate on doing everything perfectly or you will always come up short.
You are a caring mom giving unwanted piggies a loving home. Learn what you can, but don't let fear of making mistakes rule your relationship with your piggies. Learning is a life long ongoing process. I am still learning all the time. Often from things that have gone wrong, even though I have tried my best with the knowledge I had at the time.
You can't and shouldn't aim to be supermom; be sad when things don't go well - but accept that what is in the past can't be undone. It is the growing knowledge that can be carried into the future to the profit of other piggies that is crucial, and that includes making mistakes and learning from them. But at the base of it all should always be love and joy!
PS: Since we have members from all over the world, we find it very helpful if you please added your country, state/province or UK county to your details, so we can tailor any advice to what is available and relevant where you are straight away instead of having to keep it general. Please click on your username on the top bar, then go to personal details and scroll down to location. That makes it appear underneath your username i every post you make. Thank you!