Well this is a common thing we get with customers in our garden centre. one question is it growing in pot and is it yellowing a lower end of the bush. does it wilt during the day and recover a night. Sometimes i find with Fuschia is that if they allowed to try out in pot it sometimes stresses the plant out so to save on water evapatating trough leaves it drop some and you see brown scorched march round the outside. try scrapping the stem to see if itsa green under the bark.

Drought, by the sound of it - water, water, water, especially if you're in the south, it's like the Sahara here. If its in the ground, leave the hose running on a gentle trickle at the base for a few hours.