"becomes softened" is correct and usable in written English.
You can use it to describe a change in something, such as a person's attitude or a sound. For example, "The sound of the wind against the windows becomes softened as the evening light fades."
Chondromalacia patella, also called chondromalacia of the patella, condition in which the cartilage on the undersurface of the kneecap (patella) becomes softened or damaged.
As the polymer film is pressed onto the heated mold using a roller, it becomes softened (or molten stage), where it will fill in the mold cavities under the given pressure.
And yet, these images are also clandestinely beautiful: filmed in black-and-white, their harshness becomes softened and the precise detailing of their designs comes to the fore.
He had built his technique out of the drastic contrast between tightly closed positions and stretched open ones; now this became softened, blurred.
The author of "Backlash: The Undeclared War Against American Women" argues that today's working men have become softened and confused, pushed by forces they dimly understand into roles that undermine their masculinity.
A thick corn can become softened (soft corn) due to toe sweat/moisture and become gooey and smelly.
Simmer them until the carrots have become softened, about 5 minutes.
But at the higher temperature, the composite becomes more softened and plastic.
The tissues become first softened and more succulent and later extremely fragile, as an increasing amount of blood and fluid collects in them.
Starting as gamma rays near the core, the radiation is gradually "softened" (becomes longer in wavelength) as it works its way to the surface (typically, in the Sun, over the course of about a million years) to emerge as ordinary light and heat.
But you may get softened versions of that.
