They should be fine, just keep a close eye on them. They can get ill from drinking contaminated water, but I don't think just doing it once or twice will hurt them. Maybe set a timer when they're bathing and that will help you remember? That's what I have to do sometimes. Also, I'm sure they have a regular drinking water that they're used to using.
Pigeons are smart. I noticed that when something looks really dirty, they don't drink it unless they are too desperate because you didn't provide them with a water drinker. If you deprived them of clean water with the drinker, then obviously they will drink what is available to them and that is not good. I'll give them garlic/acv on their water and watch them to make sure they didn't get sick. If they drink dirty water, they will end up with diarrhea.