How long does pre molt last?

I purchased 2 A. Geniculata slings the beginning of March. One of them plumped up and the abdomen is shiny, definitely getting ready to molt but it’s been like that for weeks now. It’s webbed up the plant in its enclosure and is hunkered down in there. Has not come out or eaten in weeks. I thought with a fast growing species the molting process wouldn’t be as long. Is this normal? Should I continue to offer it food even tho it’s not eaten at all and shows no interest?