You shouldn't just be spraying with the antibiotic spray unless you can see a reason for using it.

When you look at her feet, what do you see?
Are there any sore red bits in between the toes?
Are there any parts where the hoof is lifted away from the foot, or is bulging outwards?
Is the hoof grown round and under the sole of the foot anywhere?
Can you feel any heat anywhere in any foot or any leg?
Are there any places that seem sore, where she pulls away when you squeeze?