Whenever one of mine isn't eating I first make them move, some minutes every hour, and give belly massages (most times I put the rabbit on my leg, facing me, and rock the whole rabbit). i try to entice them to eat by offering their favorite weeds, greens and hay, with some it works to hold it against their mouth until they get angry and bite into it - and sometimes keep munching.
I give them Simethicone (min. 20mg per serving) along with some water about 3 times a day from the moment I notice something is off to prevent gas causing more problems.
If I'm sure the rabbit hasn't eaten for 12 hours and acts out of character (not comming when called, not moving much, sitting loafed up in a corner or hidey house, etc.) i start syringe feeding, giving pain meds and I'm off to the vet ASAP.
Use the search term "not eating", select [search titles only] to find more opinions and information, this is a regular issue here.
That line of events in your case is unfortunate, and the cause of not eating might be different to the average case (huge hormone turmoil, stress, etc.).
If you get to the vet I would ask if an emergency spay can be done after this acute issue is sorted out to avoid a second litter.
Also, it's easier and less work to keep 2 rabbits together (at least one of them fixed) than 2 intact rabbits apart, and there are other benefits, and that's something that really sums up over 10 or more years.
Good luck.