True, what ddawn says.
Also rule out other issues - like botulism. Are you having a lot of rains lately? Any compost piles to which they have access? Kitchen scraps? Wet grain or pellets? Maggots or carcasses, such as might be found in the forest? Decaying vegetation or algea ponds?
Any access to toxins? Weed killer? Something a neighbor used that might have washed into your yard? Ant baits? fly baits?
Parasites? Check your whole flock - at night - wish a flashlight, and again in the day with a flashlight. Many parasites come out only at night onto the bird to feed and hide in the crevices of the barn in the day. Use a light colored pillowcase and ruffle through the birds' feathers - particularly at the abck of the neck and vent area. They're nearly microscopic so look very carefully over the entire bird. They can bring a bird down quickly enough (particularly in the summer) to kill them. If you find them, you must treat the birds AND the entire premises. Let us know and we can help you with that in this post.
What about nutrition? That age, nutritional deficiencies can cause this same problem. Are they eating grower now? Had they been on starter/grower? Are they eating that strictly? Do you have other birds that perhaps you can boost their nutrition in hopes of this not happening?
On all the babies, do this:
First, they should get vitamin E at 400 IU each - one capsule, slit, drop a drop into the beak. Use the same capsule for them both. Give baby vitamins daily (Enfamil non-iron PolyViSol) at 2 drops in the beak daily. Mix plain yogurt into one of their waterings. It provides riboflavin which can be deficient causing paralyzation. The yogurt will also help them digest their food better and will provide B vitamins which also, if deficient, can cause paralyzation. You can additionally crush a B-complex vitamin and give a bit of that if you don't see B in the polyvisol.
Use a boiled mashed egg yolk mixed with water and feed them that in addition to their grower/starter. You can wet them slightly to get the birds to eat them better.
Doing this multiple approach nutrition will help many nutritional deficiencies. (See this post as one possible example:
https://www.backyardchickens.com/forum/viewtopic.php?id=207448) It takes time, though.
And yes - even with a complete feed, nutritional deficiencies sometimes happen. Feed might not be stored right at the feedstore or home, or be old. Sometimes birds (particularly more delicate breeds it seems) might have a little difficulty absorbing nutrients or using them. Other birds might be from a weak line, etc.
Please feel free to email me or ask her with any questions you might have. I'll be glad to be one of the ones to help you.
