You could try watering your plants with 1. but doubt it will actually feed them. 2 - 4 don't even break down well when composted. On their own they will not feed the plant at all.

as MG says they wont on their own, but compost them and they will add nutrients to that.

Also you can buy fertilisers that are not chemically based.

I don't add egg shells to my compost any more. I find they come out exactly as they went in, and it's not a good look!
Do you add salt to the water you use to cook rice? That won't do most plants any good at all. If you do add salt, don't use the water on your plants.
Why not get some organic fertilizer as MG says. Blood fish and bone is a good slow release mixture that works well. Or if you don't fancy that you could look for fertilizer made from seaweed.

I put broken egg shells around my Dahlias as slugs do not go over them.

We don't add egg shells to compost for the same reason and Bulba isn't fond of banana skins or citrus peel either. You can buy a liquid seaweed fertiliser (at least you can in the UK), which is great. Or the good old standby blood, fish and bone as Beattie has suggested.

I always put broken egg shells in the watering cans..somebody told me to do that and I also use the egg shells round my plants to keep the slugs and snails off them, upto now it has worked.

Thanks a lot.
So, now I guess need to go for organic fertilizer.