At only 25-30 days old, there is no way that your baby Alex can be eating any types of solid food yet, he needs to be eating a baby-bird hand-feeding formula, as he will only eat liquids at his age, and he must be eating the specially-formulated hand-feeding formulas only at his age, because they contain all of the specialized nutrition (protein, fat, carbs, vitamins/minerals, amino acids, probiotics, digestive enzymes, etc.) that a baby his age needs to properly grow and develop...Without him eating a commerically sold baby-bird hand-feeding formula multiple times a day (at his age he should be eating between 5-6 hand-feedings each and every day of the formula until his Crop is full), he will soon die.
***Are you using a cooking/candy Thermometer to ensure that the hand-feeding formula you are attempting to feed him is between 104 degrees F and 110 degrees F? If the formula is even 1 degree colder than 104 degrees F he will not only likely not want to eat it and reject it, but he will also develop a terrible Yeast infection in his Crop that will make him extremely sick. And if the fomula is even 1 degree hotter than 110 degrees F, it will burn his crop and cause a horrible infection. So you absolutely MUST have a cooking/candy thermometer with a metal probe you can keep in the formula at all times while you're feeding him, and if it is any hotter than 110 degrees F you must let it cool, if it is any lower than 104 degrees F you must re-heat water and add it to the formula until it is hot enough.
***What kind of hand-feeding formula mix are you trying to feed him? He may be rejecting it if you're not using a cooking thermometer, as if you're simply using hot tap-water to mix it, that will only put it's temperature around 60-70degrees F, far too cold for him to want to eat, or that is safe for him to eat...So that could be reason #1 why he's rejecting it.
****What ambient temperature (air temperature/environmental temperature) are you keeping him in? He should be kept in a Brooder, either a proper Brooder or a homemade one consisting of a cardboard box with the back-half of the box sitting on an electric heating-pad with adjustible heat settings and that same back-half of the box covered with a towel, and it also must have a regular, digital or analog air thermometer in the back-half of the box, because if he's not being housed in a warm enough temperature he will not want to eat, and he'll develop the same type of Yeast infection in his Crop and Intestines...
A baby bird who does not yet have all of his fluffly Down-Feathers in yet (so he's still bald and showing bare skin in some areas) must always be kept in an ambient temperature around 95 degrees F, much hotter than most homes are kept, even if you live in a hot climate...If a baby bird has ALL of his Down-Feathers grown-in (so no bald spots with bare skin showing), but he doesn't have all of his mature, outer feathers grown-in yet, then he must be kept in an ambient temperature around 80 degrees F. Again, any cooler and he won't want to eat and he'll develop a terrible Yeast infection....
The temperature of the hand-feeding formula being too low, the ambient temperature the baby is kept in being too low, and not feeding the baby a commercial hand-feeding formula are the top reasons why they won't eat and reject the formula hand-feedings...Again, your bird is WAY TOO YOUNG to eat ANY solid food yet, and even if he would eat some of the seeds, nuts, etc. that you're trying to give him, they won't provide him anywhere close to the nutrition that he needs at his age, which is what the commercially-sold hand-feeding formulas provide to them, without these formulas they will die of malnutrition at his age. The most commonly sold brand of baby bird hand-feeding formula is Kaytee Exact, and also RoudyBush is very common...I don't know what type of formula you're saying that he is "rejecting", but if you're actually trying to feed him one of these commercial hand-feeding formulas and he's still rejecting it, it's most-likley because the formula is way below 104 degrees F, and because his ambient temperature is below 95 degrees F, as he's very young and probably doesn't even have all of his down in yet, and even if he does he certainly doesn't have all of his mature, outer feathers in yet, not even close....