Hello everyone! My son has light skin and his hair is also light. But …

Hello everyone! My son has light skin and his hair is also light. But only on his head do they grow in the form of dark circles. I started shaving his hair with a razor and in the upper part the hair began to darken and become stiffer, but on the nape of the neck it remained unchanged. There, even in pieces, like they don't grow at all. Because of this, he always looks like he's bald. What can be done? Or maybe you need to take tests and tell me what?