I use more or less the same system.
But i think i may have had youngbird sickness ,after asking advice on here Invincible spirit and Timbarra pointed it out to me .After talking to Spencer on the phone and following his advice i think i caught it just in time the birds are all looking good now.
I do believe Apple cider vinegar is great for keeping a lot of nasties at bay though and without it i reckon i may have had it a lot worse.