You probably did wash some electrolytes out. That’s too much water. I posted about polydipsia (psychogenic); you may want to look into that. 4 L isn’t the worst, but if it gets worse, you could get very very sick. And sodium may not be the only thing you’ve washed out.
Can you at least switch to an electrolyte drink until you get it sorted out?
When i sweat a lot i loose salt as well. Its really tricky to find the right balance. Similar with other herbs and spices, minerals and vitamins. Sometimes a bloodtest can help.
I have a rare blood disorder. I’m limited to one liter of water a day. The disorder lowers the sodium level in my body. If I drank four liters it would kill me. If you need salt in your system eating table salt won’t fix your problem except make your sodium levels too high. I would see your doctor to stabilize it.