Verbal | (loss of) vs (loss in)

I am not able to understand the usage of "loss of" vs "loss in"
I found it in manhattan guide in idioms chapter
not able to understand it fully
please explain

right:::I have suffered a LOSS OF strength. (= decline of a quality)
right:::They have suffered a LOSS IN the euro. (= decline of an investment)
WRONG::: I have suffered a LOSS IN strength.

Thanks

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