Hi Pearlie,
tight calf muscles indicates that they need to be stretched. Stretching is always a good idea, in any case, for all muscles, but the calf muscles are very important because if they are tight it can increase the probability of back injury.
I recommend that you stretch them daily, and see if that doesn't make the problem go away. It is not something just to attribute to fibromyalgia and then not do anything about it. Stretch!
My favorite, because it can be done anywhere any time and doesn't take long, is to stand facing a wall, about a foot away, and put one foot with the toes just touching the wall and then put the other foot behind and press the heel downward toward the floor. If your back foot reaches the floor flat, move it farther back, but keep your front foot touching the wall at all times, with just the toes.
Do this at least once a day (more is better) and hold the stretch for a count of 10 or 20 or whatever works for you. You should feel a strong stretch, but not pain. If there is pain just back off a bit ( you can move closer to the wall or just don't put the foot back as far) and hold a more comfortable stretch but hold it for longer. After a while you will be able to do more.
Don't know about the sore heels, and would need to know more that the word "sore" because that is a broad term that could mean a number of different things.