Mother cat hissing at 4 months old kitten after hospital visit

[natural_4u]

Hi everyone,

I have a cat that had two female kittens... Now that the kittens are 5 months old I took them to the hospital to get them fixed. The kittens stayed overnight at the hospital. As soon as I brought the kittens home the mom started hiss at her kittens. Does the mom not recognize her own or what??? I don't know what to do... they used to all cuddle and sleep together but now the mom just doesn't want them around.

Please I need some advice.

Thanks in advance!!!

Nat