It sounds like you may have an outbreak of epizootic rabbit enteropathy affecting your rabbitry. It's linked to pathogenic bacterial overgrowth, is contagious, causes jelly poop, and recently weaned rabbits will be the most vulnerable. Not a lot is known about the cause or how to treat it, but there are things that can be done to help minimize the risk.
https://www.raising-rabbits.com/epizootic-rabbit-enteropathy.html
A high carb diet for baby rabbits can make them more prone to developing GI disease like ERE because they don't process carbohydrates as efficiently as adult rabbits. The carbs make their way to the cecum, which can lead to an overgrowth of pathogenic bacteria and result in the ERE or other fatal digestive diseases developing. There is a possibility that it could be related to the feed your rabbits are getting if it is high in carbohydrates or even contaminated in some way during the pelleting process. Also if you feed any high carb supplements like oats or calf manna.
What I would do for rabbits that aren't sick yet is stop all high carb supplements, change feed to a higher quality one if possible and maybe even reduce feed amount(provided the rabbits are eating hay well), and free feed(unlimited) a good quality grass hay(no mold, no noxious weeds). A good grass hay is the absolute best thing to help prevent and correct digestive problems in rabbits, but you do have to ensure the rabbits are all eating the hay really well or it won't help.
Then disinfect and clean the whole rabbitry to help reduce possible contamination and spread.
One other possible source is if you are on well water. I've heard of some instances where owners found their rabbitry wide GI issues were linked to contaminated well water.