If you're using an Easy Cloud layer, try reducing the "smallest scale" on the Quality tab by a factor of ten and see if that makes a difference.
Although the Easy Cloud has limited control over the built-in fractals, you can add more detail and really push the values around using a Mask input. A Cloud Fractal Shader with high roughness (like 5 or higher) can add some wispy details and break it up in interesting ways. To create a subtle breakup I would give this mask shader a "Coverage adjust" setting of 1 (so its values average around 1, although lower values can work too), and play with its contrast setting to change the strength of the breakup. For a subtle wisp or detailing effect, the feature scale and lead-in scale should be much smaller than the depth (thickness) of the cloud you are affecting.