The phrase "are on the mend" is indicative of a positive recovery or improvement. Antonyms for this phrase might include "deteriorating," "worsening," or "regressing." These words suggest a decline or backslide in one's health or situation. Other antonyms for "are on the mend" might include "stagnating" or "plateauing," which suggest a lack of progress or improvement. In contrast, "faltering," "struggling," or "floundering" imply a difficult or unsuccessful recovery process. Overall, antonyms for "are on the mend" convey a sense of negative outcomes, as opposed to the positive connotation of the original phrase.