Ill get some pictures tomorrow. Although what you've said is a little reassuring that some of what im seeing is natural. It just seemed a little abrupt as for the past 3 years the tree has seemed happy, it must be coming of age!

Hi, Ive attached some photos of my orange tree,

As you can see there seems plenty of light during the day.

There are little brown spots on the back of some of the leaves which have been growing in number (not size) over the past few weeks/month

The orange tree as a whole has lost a number of leaves, and they are still dropping

There are some new shoots in places but not everywhere. On the very tips of some of the new shoots some appear slight brown rather than a bright vibrant green

However a lot of the leaves look OK hence why im confused, what every the issue is it doesn't seem completely wide spread

At first i thought perhaps over fertilization so i flushed the pot with water which once passed was brownish in colour indicating a presence of organic and fertilizer matter.

I also have a younger lemon tree next to it with slightly worse problems. browning on the leaves seems more wide spread and the new growth seems quite pale

Any suggestions?

Turned the plant and found more brown patches

What is that potting soil made of? It looks almost like pure sand. If it is then that would be your problem. Sand has very little air between the particles, and so if you water too much the plant basically suffocates. Plants need water, but also need a tiny bit of air around each soil particle.

The brown spots appear to be edema, which I think is a physical reaction to too much water. Not sure though as it's not very common in my area. Someone else may comment on that.

The paleness of the leaves, imo, is from too much water too often, and lack of nutrients. But that doesn't mean to fertilize it right now. It could also mean the roots got a little damaged from the heavy mix and lack of air, and so are not delivering nutrients efficiently right now.

If I were you, I'd re-pot into some better draining, airier mix, like Gritty Mix or 5-1-1. You can look up these mixes by doing a search on them in the forum search box up at the top.

When they recover and the roots become more healthy after re-potting would be the time to feed them. It could be several weeks after re-potting. Never feed a stressed plant.

Thanks, the mix is basically about 30% sand to 70% multi-purpose compost as i didn't have anything else. The top half inch is mostly just sand as this pretty much irradiated a fly problem i had where they were laying eggs in the sand.

Yeah, the flies were probably Fungus Gnats. That also makes me think the soil is staying too wet, as they breed in damp peat/compost. If your mix has more air and dries faster you'll not have problem with the gnats either.

How many hours of direct sunlight per day?

This time of year about 5 direct as im on a south-east facing window. Then another 6 - 8 hours light but not direct sun as its on the window ledge. I live in the UK (Manchester).

Today i replaced the top 1/3 of soil. This removed much of the sand. The soil below was damp, not moist and warm to the touch (Heated due to sun)

Below are a small section of roots i was able to carefully remove.

Thoughts?