I don't ever remember seeing juvenile Goldfinches this late in the year. I guess they have raised a second clutch of eggs this year. The young one on the right looks to me to have recently fledged:
You can tell the young Goldfinches by the missing or patchy red on top of their heads:
Here a Greenfinch is just launching itself to drop down to another feeder:
A bit of video taken yesterday with the Canon 50D running Magic Lantern.
Towards the end one decided that the queue was too long for the feeder so dropped down to try some dandelion seeds.
The black with white blobs always makes me think they are wearing a tail coat ready for a formal dinner.