Ive had my Henlei go on a somewhat hunger strike like you describe. Yes water changes you cant go wrong with and believe it or not some salt does wonders. The salt helps heal wounds and reduces the stress. I just moved my 2 males to there new tank and they ate very little. Doing daily a 1/3 w/c in a 350 gallon and adding 8 tablespoons a day of salt. Every day they get better and better. Salt is not bad in moderation.