This is from this article which sounds like it would have to be cumulative based on what I’m reading:

homepage.mac.com/mattocks/morfz/myco.html

The poisoning may manifest as on-and-off, chronic or acute episodes, depending on the amount of toxic feed ingested and how consistently it was fed. The damage to internal organs is cumulative over a period of time. A high incidence of gastrointestinal upsets (impactions, etc.) and of disease associated with depressed immune function (Pasteurella, etc.) may be clues that a mycotoxin problem exists. Some clinical signs which may appear in a rabbit:
Severe pain in the abdomen — sudden onset, haunches flaring out, belly pressed against or writhing on the floor, bunny might be lethargic and hide in a corner.
A radiograph (x-ray) series may reveal gut shutdown but no physical blockage (barium barely drips through), sometimes severe bloating. Often diagnosed as GI stasis or stenosis without identifying the underlying cause.
Standard GI stasis treatments no longer work, GI motility drugs (Cisaspride/Metachlopromide) lose their effectiveness either because the tissue along the GI tract is necrotic/damaged or because of the overwhelming deoxynivalenol(DON)-induced inhibition of gastric emptying via serotonin receptor sites.
Hypothermia (low body temperature).
Blood abnormalities: high BUN and creatinine levels, calcium-phosphorus imbalance (which may lead to chalky urine, organ calcification), abnormal levels of liver enzymes associated with kidney/liver failure; low hematocrit/RBC due to internal bleeding.
Ulcers in the mouth (strange chewing and tongue motion, difficulty swallowing, teeth problems ruled out), stomach and esophagus.
Refusal to eat, weight loss.
Presence of mucous in the feces.
Rough hair coats.
Sometimes paralysis or twitching in hind limbs.
Multiple bunnies fall ill simultaneously in the same household.
Food tests positive for mycotoxins.
An endoscopic examination may reveal ulceration along the GI tract but this procedure is difficult to do on small animals.
Necropsies may show: GI bruising (often subtle), hemorrhages, stomach/GI ulcerations, mouth ulcers, kidney/liver damage (lesions, lipidosis, fibrosis, swelling, discoloration), rectal prolapse.
While many mycotoxins can be measured in environmental samples, it is not yet possible to measure mycotoxins in human or animal tissues.

I wouldn’t be but that’s just me. You’ve done your due diligence and gotten rid of the pellets which is really all you can do and you don’t really know if there is anything wrong with them other than they turned their noses up at it.

The last bag of pellets I got was different to the previous one. Mainly the smell. I asked the feed store about this and they said it was because the hay used in the pellets had been in storage. During the hay season, the pellets manufactured did not have this smell. Another possible reason for your rabbits been fussy about the pellets I guess.