how many veggies

So I give both my girls unlimited bluegrass or 2nd cut Timothy hay placed out during the day, the measured out bowl of pellets, water bottle refilled daily, and veggie plate recommendation in long term diet spread out morning and night minus green bean they dont like it. There's never bloat or...

:help: I have been feeding my guinea pigs kale, romaine lettuce, bell peppers and carrots. But, when researching if kale stems are okay, I ran into a few sites/people that said kale should be fed once a week or two weeks even and that it isn't good for them? I was wondering if this is true...