1 regular and 2 shell-less eggs in one day...Why?

I have a 24 week old cuckoo marans hen that started laying about 2 weeks ago. She's been laying about 3 - 4 eggs a week, all looking like very normal pullet sized eggs. Today she laid one early in the morning, no problem. BUT, late this afternoon while I was out giving treats as they were free ranging, she stopped right in front of me, looked like she was going to poop and very quickly laid a shell-less egg. I was shocked, because it's my understanding that it takes about 25 hours to form and lay each egg. However I was even more shocked when I was locking them up tonight and she laid another shell-less egg right from the roost! What is going on?

I'm new-ish to chickens and did a forum search and I can't seem to find an answer as to what's happening. I feed layer pellets, they have free access to oyster shell, which I have been refilling so I know they are eating it. They are allowed to free range at least 4 hours a day. She looks good, clear eyes and nose, good red comb, I check often for mites and other crawlies and I don't think there is any stress in the coop. I checked her vent tonight with a flashlight and it looked fine. It did feel slightly wet on some of the feathers around but I'd imagine that is because it was so quick after the egg? The weather here has been 85 and under so I don't think heat is an issue.

I'm really thinking this isn't normal. What can I / should I do?

Thanks.

 

Ok thank you for the replies. I'll just wait for awhile and see if things become more normal. Sometimes I feel like I just need to be brought back down to earth when it comes to my chickens. It's ridiculous how much I enjoy these girls!