hi
i bred and showed canarys for 18 years, first thing i would check would be the parents, if they are a bit down and not intrested in the chicks then it could be a mite investation. if so the best thing for killing mite on the birds is frontline spray it is for dogs and cats, put one drop on the base of the tail just above the oil gland. this will kill all the mite on the bird within 12 to 24 hours and last for 3 months. dont worry it dont go into the birds system and is safe to use. next would to check the nest pan put a white tissue over the chicks in the pan and leave for a few minutes, remove tissue and then if there is any mite in the pan you will see them on tissue. but you will soon know if you have any red mite in your bird room by putting your face as close to the cage fronts you will soon feel them. if you cant find any mite well it could be a number of things. let me know if you find any mite or have any more problems