I give mine lettuce 2x a day and he is doing great! sometimes gets green chin but doing great! I give him green leaf, red leaf and romaine. I alternate between those three. Try a strawberry and some kale. Someone who has a piggie recommended to me strawberries, I tried it but Shadow just turned his nose up at it twice. I don't know maybe yours might like it, Spinach is good too, just a little though, alfalfa and timothy hay, any leafy green veggies provided that they are dark in color, no iceberg lettuce. I give my piggy little carrots and I also put Vitamin C in his water since guinea pigs cannot manufacture that on their own. it needs to be supplied in their diet, not too much though too much isn;t good either
hope this helps. Good luck with your piggies! post pics if you can.
lots o' piggy hugs