The white/bluish/greenish blotches? Those appear to be lichen, should be harmless, they grow when the water and air are clean. Check out the link below. They can be removed with a fungicide.

Here is a link that might be useful: Lichen

Thanks for the info. Can u recommend a fungicide?

You can scrub them off with diluted bleach, but I personally like to keep a bit of that, whether or not it's considered 'correct', as I find it more realistic and interesting.