Fuchsia love humidity so it has to be the heat. Most cultivars don't do well in heat. There are some that will survive heat better. See the list

Here is a link that might be useful: Heat Tolerant Fuchsia

you also may be over watering! i water mine in a hnging basket then using a wood chopstick i insert it as deep in the root zone as i can and check how damp the chopstick is. and once it dry(no soil comes out on the stick, similar to testing brownies) i water slowly and thoughly. here is SD i water every 5-10 days

I put 4 starter plants in 12" diameter plastic pots with closeable drain holes. In western Washington on hot sunny days I move them to the shade side of house. I feel the top soil every day, and when it feels dry (or they look droopy) I water them with a watering wand until a little bit of water comes out the drain hole. On days above 85 degrees I lightly water in the morning and in the evening. I fertilize once a week after 6 weeks. I pinch them every 2 leaf joints until 8 weeks before I want them to start blooming. Do NOT water new plants unless really dry. I lost 1/4 of my starts one year from over watering.
I have been unsuccessful over wintering my plants without a green house. The new starts I buy every year at Fred Meyers in April (5 for $3.00) do much better than my second year plants.
I would like to try 14" diameter plastic hanging baskets this year if someone knows a source online. Email is davepyro@wavecable.com.