Does well developed have a hyphen?

No, "well developed" does not typically have a hyphen when used as a phrase in a sentence. It is usually written as two separate Words, especially when it functions as an adjective before a noun (e.g., "a well developed idea"). However, if it appears as a compound adjective before a noun, it can be hyphenated as "well-developed," to clarify that the Words work together as a single descriptor.