2001 Prius limped home with red triangle warning light. 2 battery cells are 6.59v and 6.53v. 1 cell is 7.73v. All other cells are 7.82v to 7.88v. I'm going to recheck number 18 to see if it was just a bad reading. Would it be advisable to replace all 3 or just the obvious 2? Thanks!