"came down with runny stools"... runny stools is a symptom of something else.
I would not give de-wormers if the test showed no parasites. But, I suppose it can't hurt - other than, THAT might cause runny stools, too!
Runny stools for a 14 month old normally are due to ingesting something that didn't agree with them - a change in food, or a new treat (those highly-processed grocery store treats are notorious for doing things like this), or something from the garbage, perhaps? A dead thing found in the yard? some tasty "dirt"... sooooo many options!
Are you doing any training? An excess amount of training treats (especially if they're of the dried liver variety) could definitely be the issue.
When we have upsets around here, I give Denna "GI Support" pills from OnlyNaturalPet.com. It's a blend of probiotics, enzymes and slippery elm bark (among other things), and seems to do the trick for us.
... re-reading your post.... your second dog "came down" with the same thing 5 days after the first? Sounds suspicious, for sure. Could be a virus, or they found the same "dirt" pile in the yard? Hopefully no one in your neighborhood puts out something nasty like rat poison.... You'd be seeing other symptoms though, if that was the case - like a lack of energy.
For a quick fix, the bland diet with cooked rice and/or a spoonful (just 1T per meal) of
plain canned pumpkin can help 'soak' up the extra water in the intestines and firm things up a bit. I would expect the "quick fix" to take at least 12 hours. You can also fast them - i.e. skip a meal or two - to help reset the system and hopefully firm things up.
