I've planted violas some weeks ago into a full sun garden bed. for the first few weeks they grew well. But now some of the plants are flat against the ground. with smaller flowers.
Unfortunately, your photo did not come through. This can happen with over, and underwatering, and a few diseases. It just depends on how it appears.
Here are some articles for more information on Viola, and their care:
Please tell me how and when to transplant dog-toothed violets?
You can transplant them while they are dormant in late summer.
Wild violets are taking over my yard and I can’t seem to get a handle of them!!!
They are difficult to eradicate because of their rhizomatous roots. Here are tips that should help: