Based on the question in the OP, I'd say the "steepest decline" was at the start of Season 7. There were dips before that, sure, but I'd make the argument that the change from Season 6 (which I actually really enjoyed) into Season 7 was where FALCON CREST had its fastest dip in quality. The show just became too busy, too fast, and there were too many characters flowing in and out of the story.