I see that the dropping is green in color. That indicates something is not correct.
I really don't know of instant solution. My pigeons always were healthy.
When I had some sick chicken hens,, I offered them food to eat with slight addition of peoples One A Day multivitamin. Not sure what is available in your country, because the One A Day is a brand here in the USA.
This is what I did; I boiled a small quantity of noodles. The quantity was about the size of one persons portion. Boiled only in (about 2 cups) of water with no salt added. When that cooled some. I took one of the daily dose vitamin tablets, and broke in half. Added that ½ tablet to the water and noodle bowl, and dissolved the vitamin. My chickens were very much for eating noodles/pasta. After 3 days of such effort, I noticed improvement in their health.
I know pigeons are not the kind to eat noodles, but I never tried myself. Maybe if you offered them the water with the vitamins in it,,,, would possibly help.
If you do decide to experiment with vitamins,,, keep the doses very small.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,