The first thing you should always do when a parrot starts plucking or barbering it's feathers, or starts any other type of self-mutilation/destructive behavior is to get them to a Certified Avian Vet only, no Exotic's Vets at all, as you need only an Avian specialist to handle this, and preferably one that has a lot of experience in testing, diagnosing, and treating parrots who pluck, both physically and behaviorally. Red-Palm Oil is not going to do anything at all to stop or even help his plucking-issue, as Owlet already stated, but it can't hurt his overall-diet as a supplement.
A captive/pet Macaw who suddenly starts plucking at only 7 years-old is a great worry, especially if he's not been re-homed or gone through some great environmental, home, or ownership/people change, or some other change that occurred right before/around the time that they started plucking. Otherwise, at only 7 years old, it's likely a physical health issue that is causing it, especially if it's only targeted to one specific area!
***Exactly where is the "one spot" on his body that he's been plucking? This may be a huge indicator to what the cause might be.
Has he been at all sick recently, or before the plucking started? Any health or physical problems/illnesses/injuries recently? Any changes in his diet?
***Has he been DNA-tested to ensure that he is actually a male, and not a female that could be having some type of reproductive-system issue? This is also the reason I asked exactly where the "one spot" that he's plucking is located on his body, as if he's not been DNA tested, at only 7 years old this could very-well be hormone-related, but that doesn't mean it's not something you must worry about and get him help for, especially if he's actually a female.
That all being said, since it's only one location on his body he's plucking, combined with his young age, it's extremely likely that this is being caused not by a behavioral or psychological issue at all, but rather by a physical problem, and this is why it's imperative that you get him to a Certified Avian Vet with experience in plucking ASAP to rule-out a serious physical illness, injury, parasite, etc. If he's never had baseline blood-work done before to compare new blood-work to, then this is exactly the time to get not only a complete, routine blood-panel done to assess his liver function, kidney function, metabolic functions, and especially to rule-out infection, anemia, bleeding, etc., but to also have an experienced CAV run the specific blood-tests that need to be run whenever such a young parrot starts suddenly plucking. This is why it's so important to only take him to a CAV, as they know what to look for...And you want to do this ASAP, because if this is being caused by physical illness/injury/disease-process/parasite, it obviously needs to be diagnosed and treated as soon as possible, before it gets much, much worse, but also because if it's not and it's actually a behavioral/psychological/environmental cause, the plucking and self-mutilation tends to only get worse and worse. Right now it's only in one spot, so now is the time to figure it out...
