Don't know if this is to late but I would change the water straight away but it should be ok because as the water evaporates, it would not and just stay at the bottom so hopeful should not contaminate chicks. Update usI'm in the middle of a hatch at the moment. 3 have hatched- 2 have been removed and 1 has only just hatched so is in the incubator drying. But after it hatched I noticed another one of the eggs seeping! I quickly removed it and wiped the seeped liquid off the incubator floor but I'm pretty sure some of it will have dropped into the water underneath...is this going to cause bacteria to get to hatching chicks!?