Q.Why Is My Monkey Puzzle Tree Developing Brown Tips?
I have recently planted a monkey puzzle tree (Araucaria araucana) to my front garden. It gets multiple hours of sunshine every day, is in partial shade, and gets plenty of water (I live in the UK, so it rains a lot). It has started to develop some brown/yellowish tips, more and more as time goes. Could you please advise? Thank you

Certified GKH Gardening Expert
These hardy trees are very resistant to many insects, pests, and diseases. Armillaria is not one of those. This little edible mushroom is a destroyer of many trees and shrubs. The spores like it wet, so constantly wet soils are very inviting. You may notice orange or golden mushrooms growing at the base eventually. THis is the sign that the tree is on its way out. This isn't for sure but is likely, given the circumstances.
If you want further testing, Then it would be a good idea to visit your equivalent of our horticultural extension services here in the US. This article's search will not help you to find your nearest one, since it is for the US, but it will get you started in the right direction as to how to find yours.
https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm
These articles will help, as well.
https://www.gardeningknowhow.com/houseplants/monkey-puzzle/growing-monkey-puzzle-outdoors.htm
https://www.gardeningknowhow.com/plant-problems/disease/armillaria-root-rot-control.htm