Mandevillas are wilting
I live in Central Florida. I just planted 2 mandevillas in pots outside my front door. They get the morning sun until about 2 in the afternoon. One is doing great with new growth and lots of pink blooms. The other is sagging or drooping or wilting. They are in the same location, in the same size pot and soil, getting the same amount of water.
Even in the same growing conditions, plants can grow differently.
Make sure the soil is well draining. The containers can be 'lifted' from the ground to ensure excess water is draining.