under the weather vs peaked

under the weather and peaked both are adjectives.

Word	Noun	Adjective	Verb	Adverb
under the weather	No	Yes	No	No
peaked	No	Yes	No	No

As adjectives, under the weather and peaked are synonyms defined as:

Other synonyms of under the weather include ailing, indisposed, poorly, seedy, sickly, unwell.

under the weather (adjective)	peaked (adjective)
somewhat ill or prone to illness	somewhat ill or prone to illness
	having or rising to a peak