I don't get cramps in my legs often... but...

My legs often "feel like mud" when I haven't warmed up (solution, keep riding it will get better)

My legs often "feel like mud" the day after a good workout (solution, hop on bike - indoors or outdoors - and spin gently to ease the muscles)

When you are used to riding several rides each week, and some of those really push your muscles, you might also find that your legs hurt if you then miss a few rides... again, a gentle workout out a bike will appease them.

I eat well, and get lots of rest... so if you are doing both, then I suggest a good warm up (it is suggested about 1 minute for every year of your life) and cool downs... which might actually happen the next day, not just straight after the ride.

One other thought - Are you having recovery rides as well? Or does each ride feel like you are pushing the envelope? You must remember, that rest and recovery are an important part of building yourself as a cyclist...

Enjoy