Yeah, go really easy on the nuts, they are full of fat, and should not be something that is ever fed to them as a part of their regular, daily diet. They should strictly be only an occasional treat or reward, because if they become a part of his daily diet, just like sunflower seeds or millet sprays, they gradually start to build-up fat in their liver, which will result in Fatty Liver Disease, which is the number one cause of captive-birds having their lifespans cut short.
In addition to Fatty Liver Disease, Quakers have a very strong tendency to put a lot of weight on, and they do it quickly! I had this happen to my Quaker, Lita, in the first few months after I brought her home from her breeder (she was 12 weeks old when I brought her home). She was weaned onto a pellet and seed-mix diet by her breeder, which was good, but the pellets she ate were some junk-brand of pellets, and they were fruit-flavored and nothing but sugar. And her seed-mix was a really junky, Walmart type of seed-mix. So I started immediately mixing the food the breeder sent home with me with the natural pellets and the healthy seed-mix that I use. But I didn't really pay attention to the fact that she was basically just eating the junk-food and not the new, healthy food, and then of course I was giving her all kinds of treats like nuts (she will do anything for a pistachio, lol), millet sprays, sunflower seeds, and whatever food I was eating too...I took her to my CAV for her first wellness-exam the second week after I brought her home, and she checked-out wonderfully well...But by her 6-month follow-up with my CAV, well, let's just say that there was a lot more of her to love...She was like a big, squishy blob of blue and gray fluff, lol. I had never had this happen to any other bird/parrot, but Lita is my first Quaker, so I had no idea how easily they gain weight...
***Something else to be aware of is that if Kiwi doesn't eat her regular "breakfast", meaning her pellets/seed mix/fresh veggies, but then you give her "treat food" like nuts, sunflower seeds, people food, etc., then you're teaching Kiwi that he doesn't have to eat the food in his bowl, he can just wait for the "good stuff". So you shouldn't ever give him any type of treat-foods until after he eats his pellets/seed-mix/veggies, whatever his regular, healthy, daily diet is. He will absolutely be stubborn at first and seemingly go on a mini hunger-strike, lol, as Quakers are the most stubborn parrot in existence, but he won't starve himself. It's just a matter of you waiting him out; a lot of pet owners fail miserably at this, as they see their pet not eating and they immediately think that they have to get him to eat something, so they give-in and give them the junk food, and then the pet doesn't eat their healthy food. So just be sure that from now-on you don't give Kiwi any treat-foods at all until AFTER he eats the healthy food you put in his bowl first thing in the morning. And stand your ground! Don't give-in to him, and after he finally does eat some of his pellets THEN you can give him one nut as a treat/reward, but only after he eats his pellets. They are incredibly intelligent, so he's going to work-you hard over this, lol. But in the end, you have to do what's best for Kiwi's health, as you don't want his life cut-short due to preventable issues. And even if he goes a day or two without eating anything, which he very well might do, don't sweat-it, he's fine. He'll eat when he gets hungry enough, and after he finishes finally eating his pellets, then make sure that you praise him and give him a nut to let him know that from now on he will ONLY GET TREATS after he first eats his pellets.