Why would my stools turn rock hard overnight? i eat 20-35g fiber and drink 8-10 glasses of fluids a day. daily brisk walking as well.

Dehydration?: usually stools which are rockhard could a sign of dehydration. You may consider continuing your normal fiber intake, but increasing your fluid intake for the next few days. You might also review any medications you have added in the last few days, to see if they may be contributing. Good luck.

Constipation: Some people have habitual constipation. You are doing everything right to avoid it. Ask your doctor if he could prescribe you Linzess. If not, try 2 pills of Swisskris every night (available over the counter).