Had a season like this 2 years ago (on my old acc). Was all excited about it, team with mostly 4* players and bam, relegation. Still no idea why...So on way to go could be to just tank this season and bounce back on the next one.

And about players, I've noticed that if buy some new stronger players but keep your most trusted players set to take free kicks, corners, penalties both new and old players drop in performance. So check again who has the best crossing (for corners) and best shooting (for free kicks) and set them to take. Obviously if you have a SA free kicker or corner taker set him as first option BUT(!) a player with SA is usually useful only if he's higher than 3*.