Here's why:
* They are not compound adjectives: A compound adjective is two or more words that function as a single adjective. Examples include "high-speed" or "long-term." In these cases, the hyphen is necessary to avoid confusion.
* They are adverbs modifying adjectives: "Well" is an adverb modifying the adjectives "nourished" and "developed."
Examples:
* The well-nourished child was full of energy. (Incorrect)
* The well nourished child was full of energy. (Correct)
* The well-developed muscles were strong. (Incorrect)
* The well developed muscles were strong. (Correct)
Exceptions:
While generally not hyphenated, you might hyphenate these terms if they precede a noun and function as a compound adjective:
* A well-nourished population.
* A well-developed plan.
In these cases, the hyphen helps clarify that "well-nourished" and "well-developed" are acting as a single adjective describing the noun.
Ultimately, the best way to determine if a hyphen is needed is to consider the context and the overall clarity of the sentence.