You don't need to keep all of the candles lit, just try not to get down to only one. They don't regenerate if the candles go out; you just start taking more damage and can not attack them.
Do you have your creature active, and a summon, if available (summoning skill bonuses can show up on jewellery)? They may not do a great deal of damage, but they can help, and will at least provide alternate targets, so you should have an easier time switching between attacking spectres and relighting candles.
If you come back at a higher level, with better equipment, being able to do damage faster will make it easier to deal with the spectres.
