soft spot vs weak spot

soft spot and weak spot both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft spot	Yes	No	No	No
weak spot	Yes	No	No	No

As nouns, soft spot and weak spot are synonyms defined as:

Other synonyms of soft spot include weak part.

soft spot (noun)	weak spot (noun)
a place of especial vulnerability	a place of especial vulnerability
any membranous gap between the bones of the cranium in an infant or fetus
a sentimental affection