Phlox do not require shade, they are sun-lovers. You are showing flowers that are “single” but the description says they are “double”. Hmmm.
Hi there. We’ve updated the suggested exposure to “Requires full to partial sun.”
They’re called double blooms because the blooms contain two colors.
A double flower on plhox would look like a rose on each bloom. What you have is a bi-color phlox. Quite a difference.