Are Bruises On The Leg A Concern When Sodium Levels Are Low?

My husband is 14-year post Stage 4 Throat CA, has a permanent peg placement and is now very active. Prior to him being active he was passing out a lot and doctors could not figure out why. He was finally sent to a heart doctor who after many tests, said his heart was very healthy but he was severely low on sodium. He told him to put 1-2 bottles a day of Gatorade into his tube as tolerable. Well it works extremely well ...He bike rides 15-20 miles q 3-4 days and has been walking 4-7 miles q other 3-4 days (and rides a stationary bike if too hot to go outside). Here s the problem, he has what looks like RED bruising climbing up his legs starting at his ankle and up his calf. We have no idea what is causing it and it s concerning me! He put some cold packs on but the change is minimal. Any idea what is happening and should we be concerned?