no expert on java sparrows although i do keep them,breed them/ this note is made using 20 years worth of hand rearing and observations with regards to chicks reared and birds bred ....
red tips on the wings can be a sign of dehydration, check to make sure the chicks body is not a very pale yellow/white color ..
however bleeding on the wingtips is usually in my experience the parent birds pecking at the chicks, try removing the cock bird as he may be trying to persuade the hen to start another clutch.. if the chicks are still been found to be bleeding then the culprit be the hen, in which case i would stop her from breeding altogather but that is just my oppinion,
how many nestboxes are the birds provided with, i would recommend 2 and a half nestboxes per pair of birds if in a flight, if in a cage on their own then 2 nestboxes this would allow the birds to start another clutch and encourage the cock bird to look after the chicks while she restarts another clutch, ...
also in case of dehydration which can also make the wing tips red and bleed, always make sure to feed moist eggfood, the tips of the elboxs are usually the first place to be noted when dehydration occur they turn red and the skin drys out , when the skin drys out it can crack and break the skin open which causes the bleeding,
add some corn flour to the bleeding area to help clot the skin up and stop the bleeding... weather or not you find the cause of the bleeding ..corn flour is a good way to stop the bleeding their and then...once it stops bleeding you can also add a bit of vaseline on to help the skin incase something is rubbing on it or drying the skin out and causeing the bleeding ...
and hi poohbear fancy meeting you here
:D