Hopefully someone else has seen this and responded. However, she might be egg-bound. Sometimes, if the egg isn't far enough down for the vagina to start turning inside out and blocking off the intestinal track...the force of the contractions can squish some poo out. cecal poo looks yellowish.
Can you feel and egg there? Gently lift her/hold her, and feel abdomen..and, with a lubed finger...if you aren't sure with the feeling the abdomen, insert one finger into her cloaca. If she is egg bound, you should feel the egg with your finger going in 1' at most. If she is egg bound, sometimes a warm 'sitz bath' and some gentle lubing around egg/cloaca may help. Also, if she is egg bound, try to give her some calcium. (mashed tums made into a slurry with water is a start.
@RoyalChick or
@Kris5902 and/or
@BY Bob can probably give more specific assistance and or other suggestions if she isn't egg bound.