On my home computer, I can see that they still have some downy chick squiggle feathers sticking up. My guess is they are about three and a half weeks old. Does that sound right to others? There are a couple of feeding methods that one can use. The first one is forced with a tube (specially bought metal feeding "needles" can be used, or small latex or other soft tubing which they sometimes have at lowes even). Risks are puncturing the crop lining, feeding to much and risking aspiration due to vomiting, feeding too warm of formula and not easily being able to detect hot spots, and going down the trachea instead of the esophagus. Pros are that it is cleaner, takes less time, and you can more easily measure food. I'd say it'd be overkill in bird this age.
To reduce the risks of tube feeding, many prefer methods that let the bird eat at its own pace. For young squabs, a syringe with the tip cut off and rubber placed over the tip with an x cut in out allows for natural beak in beak feeding. For birds more this age, they will probably peck at seeds with encouragement, and formula can be dropped from a syringe or fed from a spoon to help get in enough food and liquids. Sounds like they already are drinking water, so a few hand fed peas to whet their appetite may be enough to get them started going after seed. Small, millet mixes are a good starter for pigeons while they get the hang of eating. If the crop feels too hard, you'll have to step in to get more liquids down them. I find, for whatever reason, stroking the back of the neck gets a young bird to start pecking at seed.
. At least, that is what I have found. Seems everyone does it differently.
Man, those colors are so gorgeous together, whatever they are.