I know that they appear to be different somehow, and in many ways they are, but just like other fruit trees, Cirtus trees needs pruning also.
The best approach I have found with citrus is NOT to undertake infrequent heavy pruning, as that can lead to aggressive upright growth. If you take a lot off, the tree will try to replace the lost foliage.
To avoid this, it is better to undertake regular small amounts of pruning, taking off less than 1 quarter of the overall tree, which helps it avoid shock, and reduces the risk of it regrowing heavily. Prune them all year round to get rid of new growth (unless you want them to grow big) enabling them to produce fruit with minimum growth.
So go out and have a look at your lemon, orange, grapefruit trees (these are the ones we have) and give them a light prune if they are looking a little top heavy.
And while you are out there, check out your other fruit trees as you many need to thin out any new growth they have put on above the fruit, as that maybe stopping the sun getting to the fruit, making it hard for them to ripen.
I think we have sun this weekend, so I will certainly be out there playing around.
Enjoy
Peter