Ouch. can anyone help?

Lately my quads and calves have been getting EXTREMELY sore. I'm a rower and I also run, so I need to figure out what is causing this. It just started a couple of weeks ago, despite the fact that I have been exercising at a high intensity level for years without a problem. I also eat well, high protein, lots of fruits and veggies, and rarely any junk food. I'm wondering if maybe it has something to do with dehydration. I probably drink about 80 mL of water a day. Do I need more? Can lack of fluids cause this muscle soreness?