The plant was 3or4 years old when I bought it online. It looks very healthy.
That will be hard to say. Its fruiting capacity will be directly correlated with the care that it receives. If this was just potted and the roots have not completely filled out the container, then you can expect fruit set in a few years. Most of the time, it will drop all flowers and fruit until it is established enough to produce.
Here is an article that will help you to help:
https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees-in-pots.htm
why are my ripe kumquats dry
It seems that a kumquat tree takes the water for itself first before sending it to the fruit, so if there has been inconsistent watering, it could result in dry fruit. But another reason could be that the fruit is being left too long on the tree before being picked. This article outlines the best growing conditions for your kumquats: https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees.htm
I see no insects or spiders. What is this and how do I treat it?
This is from spider mites. Spider mites are so tiny they can appear like a dusting of pepper on the undersides of leaves.Treat your tree with neem oil to stop the spread of these pests. https://www.gardeningknowhow.com/edible/fruits/citrus/citrus-mite-problems.htm
Had this tree for 6 months, water 1week or 2twice in hot weather, 1 half growing mad but the the rest the leaves are dropping off. Soil not wet, I water from the bottom and feed once a month. Back room south facing it is in there. What am I doing wrong and will I loss my tree. Hope you can help me.
Perhaps watering from the bottom is causing root problems. Our experts say kumquats don't like wet roots and they need air circulation under the pot. Check on your growing conditions based on this article: https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees-in-pots.htm
Also, this article will explain kumquat problems: https://www.gardeningknowhow.com/edible/fruits/kumquat/kumquat-not-flowering.htm
Yellowing leaves. Can these trees be pruned? They are 12 years old. Become too big for the garden bed.
It is very hard to see from the photo. Close ups of the leaves will be telling of the exact deficiency. In the meantime, you will need to do a soil test. This will tell you, exactly, what the tree needs.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees.htm
I love this tree and it’s produced abundant blossom and fruit but I feel like I’m losing the battle with the yellowing leaves. It’s produced new growth so it can’t be under watering. But I’m confused if it’s overwatering - root rot or zinc / manganese deficiency. Please help!!
It could be a number of issues. I can't see the soil, so I can't confirm under/overwatering, though overwatering is a lot more likely. This will suffocate roots, and appear to be many deficiencies.
You can cut all doubt, however, by testing pH and nutrient content, and by testing soil moisture.
These articles will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/test-soil-for-pests-and-diseases.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/making-sure-soil-drains-well.htm
This article will help you to care for your tree:
https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees.htm
They are currently turning orange.
The fruit should be plump, bright orange, and firm. The time of year depends on the cultivar. In Australia, the trees usually ripen in the cooler months.
https://www.gardeningknowhow.com/edible/fruits/kumquat/harvesting-a-kumquat-tree.htm
https://www.gardeningknowhow.com/edible/fruits/kumquat/growing-kumquat-trees.htm