Why is my puppy such a prolific pooper?

For the last two days or so my puppy’s poop output has increased dramatically. She used to go once or twice each day. Now she goes…well, a lot more often than that. I’m not looking for a diagnosis, but some leads would be nice. And yes, I’m going to contact her vet. It’ll be a few days before I can get her in, though. Besides, I know how much y’all love poop-related posts…

By the way: The pup is a 6 month-old schnoodle (schnauzer/poodle).

It started Monday night (aka Tuesday morning). She woke me up at 1:00am and 3:30am and pooped both times. She acted very urgent about the whole thing. She went again when we got up around 6:00am. Then she pooped in the house while we were at work, she pooped again at 2:30, again in the house between 2:45 and 5:15 when nobody was home, and again at 5:30 or so.

Last night (aka this morning) she went twice within 15 minutes (get up, go outside, poop, go back to bed, frantically beg to go outside again, run outside, poop again) around midnight. My mother stopped by my house to let her out at 2:30 and there were 4 distinct piles on the kitchen floor. I can’t wait to see what’s waiting for me when I get home.

I can only think of three things that have changed recently.
[li]On Monday night she ate a grape that had fallen on the floor. I’ve read that grapes can be toxic to dogs, but a single grape shouldn’t cause a problem.[/li][li]My wife (a teacher) went back to work, so the pup has been home alone longer than usual.[/li][li]I’ve taken the pup on walks (.75 - 1.25 miles) each of the last three mornings, plus one walk Monday evening, whereas previously our walks had only been in the evenints.[/li][/ol]
Her food and water input have not changed, she hasn’t acted ill, and her poop appears relatively normal except that it’s a little on the soft side.

Any thoughts, folks?

What’s her feeding schedule like?
If you just leave the food out and let her eat at will you’ll have problems.
Feed her once a day at the same time every day. If she refuses to eat within a half hour take the food away and don’t give it back till the next day at the same time. She’ll get into a routine hopefully.

Ahh, a good question I meant to have already answered. She gets 1/2 cup of dry food in the morning (6:15am or so), another 1/2 cup in the evening (5:30pm). She also gets a small biscuit when we leave for work (7:30am), and an additional treat or two here and there “just because.” I don’t know her exact weight, but she is probably in the 12-14 lb range.