Experts and BHG readers answer.
White spots on lantanas
Sometimes Lantanas can ooze a sappy substance that turns white on the leaves. That's my only guess. This plant is normally pretty carefree without lots of pest problems.
It can cease to bloom if it is overfertilized and/or watered, so try to let it dry down a bit, and don't fertilize. A touch of summer stress often brings out the bloom in some plants.