Hi, Garrett, welcome to the forums and I am sorry about Duddly.
I understand you have taken your bird to a vet several times but do you know is it an avian vet? And do you know what tests have been done on the bird from a health perspective?
Plucking can be psychological but there are lots of other reasons why a bird might pluck that have to be ruled out first:- Disease, parasites, infections, metabolic disorders
Your bird would have to have blood work, fecal tests, etc. to rule these out- Malnutrition or vitamin deficiency
Blood work and other tests an avian vet can do can rule this out, as can changing the diet if the diet is poor- Dyes and preservatives in food- Poisoning by heavy metals
Brass, lead, zinc- Allergies
Food or environmental allergies can cause plucking- Hormones or reproductive/sexual frustration- Dry air
If you are running the heater a lot or live in an arid environment the humidity in the air could be too low and could cause dry, itchy skin. In this case you could run a humidifier or give the bird a bath every day (possibly with a mixture of aloe and water)- Insufficient sleep
Birds need about 12 hours of undisturbed sleep per night in a quiet, dark location- Lack of natural sunlight
Sunlight through a window is filtered and the bird has no source of UV light unless it spends some time outside in unfiltered sunlight. Some birds stop plucking when they are given some exposure to natural sunlight.
If you can rule out all of the above it's probably psychological, and those reasons would be:- Boredom- Wings clipped/inability to fly- Emotional issues
Just based on what you have said so far malnutrition or vitamin deficiency can't be ruled out because a mix made up of mostly nuts in addition to fruit loops would be nutritionally deficient in many areas. I don't know if "those colored food for birds" is a type of pellet but if it is do you know how much of the diet consists of the pellet versus the nuts? Artificial food coloring and preservatives found in some pellets has been known to cause plucking.
Cage size is a potential issue; 20 inches wide x 19 inch long x 32 inches high is too small for a cockatoo, and even more so if he is spending lots of time inside of it. It really should be more like 3 ft x 3 ft x 3 ft.
My brown-headed parrot plucked for about six months and we took him to an avian vet and he had lots of tests done to rule out physical reasons. The vet thought it might be hormones so he had some injections but that didn't stop the plucking. I also ruled out all the other reasons on the above list including boredom (he has lots of toys, lots of out-of-cage time and lots of human interaction) and inability to fly (his wings are not clipped) so I was left with "emotional issues" and I had no idea what they might be.
I had exhausted my options but while reading around online I came across clicker training and I hadn't tried that yet. I didn't do anything special in regards to the clicker training (I just worked on targeting and training simple tricks like turn in a circle and wave) but within a few weeks he completely stopped plucking and it has been almost a full year now since he last plucked. There is no doubt in my mind that whatever issues he had went away when I started doing clicker training with him; I still don't know why he was plucking but I am convinced it was the clicker training that made him stop.
If your bird is plucking during the day while you are around you can use clicker training to re-direct their attention to toys instead of their feathers. Mine was only plucking at night while he was covered, and never during the day, so I was not able to use this method but most birds that pluck do so during the day and if you use clicker training to encourage them to leave their feathers alone and play with toys you can sometimes stop the plucking (unless it's health-related).
Good luck with your bird and please keep us updated!
Lastly on an unrelated note:
garrett3999 wrote:the conure is exactly like a chiwawa and thinks hes the king of the amazon LoL!!!!!
Oh, yeah, I have one of those, too!