The Eclectus parrot is said to be one of the hardest parrots to wean. If it isn’t done correctly you can end up with some behaviours & severe weight loss. Stunted & malnourished chicks are on the increase with hand feeding today. Many hand feeders use their own home made formula, never weigh the bird so never know weather the bird is actually a proper weight & healthy. You can't judge by looking at a chick & the most accurate way to know how the chick is progressing is to keep a weight chart. If the weight declines you at least can be aware this sooner rather than later.
Other causes are watered down formulas,
incorrect mixing of formulas & unhygienic areas where the food is prepared.
Pulling eggs from the parents can also cause many problems. The first 28 days are the most important to the chick because this is the time their growth rates accelerate. For this reason alone they should be kept with the parents. Only they can give the chicks the correct nutritional requirements for successful growth.