Humphrey's Homeopathic Veterinary Specific Bottles

My dad must have dug these when he had that hobby. They all differ in several ways:
All show different looking horses.
On two, the horse is looking to the right.
On two the embossing under the horse says, "VETERINARY SPECIFICS", but on one it just says, "VETERINARY"
Necks are different sizes and styles.
All are about 3.5 inches tall.

I wanted to know if this plays any part in determining the order/age in which they were manufactured.

 

I find clear glass difficult to photograph. It always seems to get reflections. I tried indoor lighting, outdoors, dark and light backgrounds. This is about the best I could get. I do have them individually photographed:

 

Your photos are good. Glass is very difficult to shoot for me too.