Brambling disease?

Trichomonosisis the disease that radically reduced the Greenfunch numbers. You say they are dying.....as in the birds look lethargic, weak, sleepy, fluffed up, have difficulty breathing, are reluctant to fly, hang around bird feeders and attempt to eat. They physically cannot swallow food or drink??
They are part of the finch family so it's very possible.
It would probably be best to remove feeders for now and give them a good clean.
You can also contact the BTO should you wish to do so...

www.bto.org/.../garden-wildlife-health

If you have a picture it may help with diagnosis

I always clean my birdfeeders every few days along with my bird-table and bird bath. As usual as I’ve had problems with my internet being able to post links. Hope the link will work!

www.rspb.org.uk/.../

The link is now working! Tried 4 times. Now the link is working!