I've never heard of it being called a Million plant before.
It's botanical name is Hydrangea macrophylla. And it has downy mildew on the leaves (that is a fungal disease)
To get rid of the downy mildew, mix one part of full cream milk with 10 parts water along with a drop of dishwashing liquid (this helps the mixture stick to the leaves) and spray it over the foliage.
You may need to do this a couple of times over a week to clear it up.
Happy Gardening
I'm confused myself why locals here call it million :D but thanks for the name and the tips... will do it if ever I see any downy mildew.