S: (v) inflame (become inflamed; get sore) "His throat inflamed"
S: (v) sicken, come down (get sick) "She fell sick last Friday, and now she is in the hospital"
S: (v) devolve, deteriorate, drop, degenerate (grow worse) "Her condition deteriorated"; "Conditions in the slums degenerated"; "The discussion devolved into a shouting match"
W: (n) slippage [Related to: slip] (decline from a standard level of performance or achievement)
W: (n) drop-off [Related to: drop off] (a noticeable deterioration in performance or quality) "the team went into a slump"; "a gradual slack in output"; "a drop-off in attendance"; "a falloff in quality"