Definition of "welk"

As gentle Shepheard in ſweete euentide, / When ruddy Phebus gins to welke in weſt, [...]

1590, Edmund Spenser, “Book I, Canto I”, in The Faerie Queene. […], London: […] [John Wolfe] for William Ponsonbie, stanza 23, page 9

[T]he Church that before by inſenſible degrees welk'd and impair'd, now with large ſteps went down hill decaying; [...]

1641 May, John Milton, Of Reformation Touching Church-Discipline in England: And the Cavvses that hitherto have Hindred it; republished as Will Taliaferro Hale, editor, Of Reformation Touching Church-Discipline in England (Yale Studies in English; LIV), New Haven, Conn.: Yale University Press, 1916, 2nd book, page 257

But nowe ſadde Winter welked hath the day, / And Phœbus weary of his yerely taſ-ke: / Yſtabled hath his ſteedes in lowlye laye / And taken vp his ynne in Fiſhes haſ-ke.

1579, Immeritô [pseudonym; Edmund Spenser], “Nouember. Aegloga Vndecima.”, in The Shepheardes Calender: […], London: […] Hugh Singleton, […]; reprinted as H[einrich] Oskar Sommer, editor, The Shepheardes Calender […], London: John C. Nimmo, […], 1890, folio 44, verso