the leaves started turning brown quite recently, it has full sun during the day (moved it into the shade better picture) but the leaves are turning brown and curling up, I water it regularly
Any ideas?
in zone 8b, it does get down to 8-9'c at night now

Not sure if it's politically correct to suggest a different forum but since I notice you didn't get a response.....try the TropicalFruitForum

I got a quick (and excellent!) response to the question I had about my passion fruit vine!

I think your overnight temperature is way too cold for your mango tree.

Mango trees typically loves a sustained 70F or higher temp with high humidity and direct sun.

You may want to consider using grow lights to control its growing environment especially as we head into much colder season.

It can actually dry between waterings so it could be too wet.
But more importantly, they need 70F and up. Cool temperatures cause leaf drop and fruit loss! 8-9c is much too cold!!!
They need full, strong sunshine.