I’m not an expert, but outside of a specific health condition (none specifically come to mind) it could be a few things potentially.
What does eating “relatively ok” mean? It’s possible you’re not getting enough from your diet. Sodium and potassium, could simply mean drink more lucozade and eat more bananas.
Maybe you drink too much water, which can lead to tiredness, fatigue etc because you have too much. Water helps to keep everything flowing, and that could be diluting the sodium within your body. Not sure about it’s impact on potassium, but could also be the same.
It’s worth just going over your regular diet) and reviewing the nutrients and vitamins you’re getting in these and see what’s missing and how you can add them in