Beet-sugar producer Holly Sugar Corp. said it was renegotiating a possible price reduction and other terms of its takeover by Plum Associates. Last month, Holly agreed to a sweetened, $95-a-share offer that values the Colorado Springs, Colo.,-based company at $106.5 million. Plum, an investment group, first bid $91 a share or about $102 million. However, on Oct. 29, the two companies said they had discussed a proposal by Plum to reduce the purchase price to $85 a share because of the reduced value of Holly stock since the October stock market collapse. Holly said at the time that it did not accept the proposal.