Mine get veg twice a day plus a little cucumber night night tidbit.
Please feed fruit and tomato only twice a week. Too much oo often can cause sores in the mouth and on the lips. Also vary between peppers, broccoli and fresh herbs; one variety per day is enough. For instance, 1-2 stalks of fresh herbs contain all the vitamin C and minerals that a piggy needs in a day. You can grow your own herbs on your windowsill.
Kale (which is a variety of cabbage) is very high in calcium and should not be fed too often; the same goes for spinach and any Asian cabbages. other cabbages like pointed/sweetheart cabbage, spring greens or savoy cabbage are not quite as high in calcium and can be fed in small quantities as part of a mix.
Guinea pigs have a naturally high alkaline urine and are more prone to urinary tract problems and bladder stones than other species. Ideally, you feed a bit of everything in moderation. What you have to aim for is a sensible and practicable balance of what your piggies will eat, what is practical and how much you can spend.
You can also feed: fresh beetroot (counters calcium) preferably without the leaves, sweet potato, chopped celery stalks, cucumber, sweetcorn (with husks) or baby sweetcorn, green beans and mange tout (the pods), fennel, chard, organic banana skins, strawberry greens and leaves.
Here is a chart of all the veg, herbs and fruit that guinea pigs can eat:
http://www.guinealynx.info/chart.html