Connie,
Is the top leaf still turgid? If so, it was probably "reaching" for the light as phals grown in windowsills often do. If the leaf is stiff, there probably really isn't anything to worry about.
As for the red coloration, it just might be too bright, especially for a
phal in bloom. The blooms on my phals last longer when they are out of the hot windowsill sun but still in good indirect light.
How about a close up of the leaf in question? That may help.