i'm not so good with the latin names & some may just be what i call them as a localised name,but i know that guineas can be fed or i have fed in the past
some of the following
plantain (wide & narrow leafed varieties), Yarrow, daisies, cleavers (stickybuds plant), bramble/blackberry leaves although i usually squash/knock off any hard prickles, but they love the young leaves with no prickles, dandelion (whole lot, flower,stem & leaves), groundsel, raspberry leaves, milk (sow?) thistle, cornsilks (stringy bits between maize cob &leaves, mine go nuts for them).
marigold leaves, rose petals, fennel & echinacea.
i think the general rule of thumb is if its come from a bulb it is poisonous/harmful to guineas. eg Buttercups (apparently ok if fed dry in hay)
i dont usually feed dock as this has a high oxalic acid content which contributes to kidney/renal problems (higher acid content after the flower stems appear & the stalks are woody).
watercress can be given, but i would be careful with it fresh out of a stream as they are apparently prone to a "fluke" i think its liver fluke that attaches itself to the leaves & then comes off when inside the animal & attaches itself there. so i would personally just stick to watercress grown for human consumption or check it thoroughly first!
just check that the plants dont have any mould or mildew on them & give them a quick rinse off to wash off any dust, debris & insects. x