GST on body corporate fees?

I have two investment properties, and the body corporate is administered by a different organisation for each property. The body corporate fees on the first property do not have GST added. However with my second investment property (just purchased) the body corporate fees, both for admin and sinking fund, have GST added. They give a 10% reduction for early payment, and then add 10% GST. Paying GST raises the body corp fees by $200 per year. I don't pay GST on rates or water so I didn't expect to pay them on my body corp fees either, especially for the sinking fund. Does anyone know if it's correct to pay GST on body corp fees? Why would one body corp company charge GST and the other not?