My kumquat true which is always prolific, seems to be suffering from something. It is loaded with fruit, but only the fruit at the top of the tree and on the north-west side is orange. The rest, although full size looks as if it has been frozen. But, We have not had a frost.
From this description it is difficult to know if you have a disease or insect issue.
It very well could just be that some of the fruit is not ripe yet.
I am listing several links that will help you pinpoint the problem.