A low pH can certainly affect the luciferase system used in all of these products. The luciferase will not work if the pH is below 6.5 and performance will rapidly decay below pH 7.2. The reagents in these kits will buffer back to some degree but obviously if the pH is very low it will not be able to do this adequately.
ViaLight™ Plus Cell Proliferation and Cytotoxicity BioAssay should be the least affected by this as it works by acidifying the sample and then has a very strong buffering system to bring the sample pH back into a usable range.