The tulips are too dark of a pink to really work with your theme. I definitely think doing some white will help, especially as it has a more pastel vibe.
This.
I think the roses look a little off with that theme you're going for.
I have pink roses next to pink Hydrangea and Pink Azaleas and they look great, but that's because I think that's because the Hydrangea are dark-leaved and the roses look good next to them.
The Cosmos just look nicer with the Azaleas, In my opinion.
The tulips are too dark of a pink to really work with your theme. I definitely think doing some white will help, especially as it has a more pastel vibe.