No a seed only diet isn't good for them. Try some mixed veggies and mix seed onto them. While your birds are eating the seeds they will also get a nibble of the veggies along with them and might decide they are good. You can also mix up some sweet potato, peanut butter and banana and roll it into some seed as well. Any veggie mixture will do as long as you have the sweet potato in it to keep it sticky.
You can also weave things like kale, and other greens into the cage bars. Keets love to nibble on things so this might spark some interest as well. Nan. P.S Fabio is beautiful!!!