This is our first shih tzu and reading up informs us the 1st season occurs between 6-9mths. Holly is not quite 6mths yet but we have noticed blood spots on the bedding. Could this be her 1st season or could it be any other health issues?

Sounds exactly like her first season. Holly obviously hasn't read the books! ;)

For the next 21-28 days keep her away from all other dogs; don't let her off the lead, and don't walk her in places where you're likely to meet other dogs. Don't let her into your garden unattended, no matter how secure you think it is.
:)