YOU SAID:

They have lost their calm.

INTO JAPANESE

彼らは冷静さを失っています。

BACK INTO ENGLISH

they're losing their cool.

INTO JAPANESE

彼らは冷静さを失いつつある。

BACK INTO ENGLISH

They are losing their cool.

INTO JAPANESE

彼らは冷静さを失いつつあります。

BACK INTO ENGLISH

They are losing their cool.