Discolored Areas In Legs. Are They Bruises? Took Levothyroxine. Why Tight?

I am a 62 year old female. About 6 months ago, I noticed discolored areas on my lower legs. At first I thought they were bruises, but they never went away. They were reddish in color but never itched. My GP did bloodwork a couple months ago which all came back OK. I do take75mcg Levothyroxin but no other prescription medications . I am not obese and I am a runner. In the past few weeks these areas have become increasingly smooth, shiny and tight. There is no swelling but I can feel the tight sensation, especially when I flex my leg. The skin feels harder and smoother than the surrounding area. This makes my lower legs feel tight and constricted. Help, please.