That is good, to not put them together it is very vey dangerous but I am happy to hear they arent.
Well you can feed them Romaine lettuce(not other types), parsely, red/green/yellow bell peppers, kale, carrot tops, brocoli, outer leaves of cabbage (inner leaves are too watery), corriander, cucumber, spinich (small amounts), carrots, apples and oranges this is what I mostly give my guy.
All fruits must be given very rarely as the acid in them can give them sores on the side of thier mouth, maybe every week or twice a week and only a small amount at that. Somethings like cabbage, kale, brocoli should just be given every second or third day and not a whole lot at that as they are gassy and guinea pigs dont pass gas so can make them sick and even be fatal. Spinich is high nutrients so please just feed it every odd time. My guy actually doesnt like this. Just give him a very small amount the odd time. Carrots too shouldnt be fed a whole lot as they have natural sugars in them. Red bell peppers should only be fed once a week but they are good to feed once a week as they have alot of nutrients and vitamin c so try and feed them once a week. Yellow bell peppers can be fed every day if you wish, green bell peppers can be fed every two or three days. I would though suggest not feeding things every day even if they are safe as your guinea pig will get bored.
Some things are posion and should be avoided like lettuce(except romaine), potatos, tomato leaves, onions, chocolate, 'human food' etc.
I will try and find a good website for you on vegetables as there is alot you need to know and hard to type it all LOL..
Oh and ill explain more about introducing slowly. For example buy some romaine lettuce, give a small amount and then watch for loose stools, swelling, any unusual behaviour, if none after 24 hours then give another amount, slighly bigger amount this time, again wait 24 hours then you can feed it normally. Then after the two days (experts say 24 hours i like to wait 48 hours) go and buy some for example again some parsely, do the same by ggiving a small amount when you feed the romaine to her. Watch for signs, wait 24 hours, give some more, wait 24 hours, then you can introduce the next thing.
Rabbits and guinea pigs are quite common in the whole feeding thing. Just for guinea pigs need vitamin c more than rabbits and guinea pigs eat alot more than rabbits and need about twice as much veg as a rabbit. I feed my rabbit about half a cup of vegetables which i feed my guinea pig a full cup of vegetables a day. I also leave pellets out full time for the guinea pig and just a small amoutn for the rabbit in the evening.
I will try and get you that website