What specifically did PetsMart test for? Would it be possible to get your own test kit and record the actual numbers? Bringing in a water sample is useful for getting a general idea but all aquarium owners should really have their own way to test.
While the bottled water didn't help, that wasn't your main problem. This is essentially what happened:
-A brand new aquarium was set up but not cycled (aquariums have to be cycled before you introduce animals...pet stores love to leave that part out!).
-The tank was stocked too quickly with too many animals (I would keep 5-6 frogs MAX in a 10-gallon and they should be added over time).
-Ammonia built up, followed by nitrite, since the tank lacked the needed beneficial bacteria (cycling an aquarium is basically just a process to make sure you have some beneficial bacteria to start with). Ammonia levels would have been very high at this point (because of all the frogs), had you tested for it. This would have undoubtedly stressed the frogs (and would have killed most fish), suppressing their immune systems.
-The aquarium finally started to cycle and stabilize. You got your first bacteria bloom (the good guys who turn toxic ammonia and nitrite into fairly safe nitrate), hence the cloudy water (it wasn't actually a sign of something bad).
-Unfortunately, you accidentally killed off most of the new bacteria by changing the filter pad and doing large water changes. The filter pad shouldn't be replaced very often, it can instead be rinsed occasionally with water. That way you keep some bacteria. You should never clean out the filter the same day as a water change--it removes too much of your bacteria at once, without letting the system recover.
-The aquarium starting cycling again and so the cloudiness stayed as you got another bacteria bloom. Your water parameters were ok at this point since the bacteria started being able to keep up with the ammonia and nitrite (the loss of a few frogs helped this since your tank was now more reasonably stocked).
-The well water and spring water may have had different pH. It was a good switch to make but the switch should have been more gradual. pH shock may still be affecting the frogs but the best you can do for that is wait and see what happens. By cleaning out the whole tank, however, you killed off the bacteria again. This means that you'll begin having (or already have) ammonia spikes...followed by nitrite spikes. Both compounds are very toxic. The aquarium will need to re-cycle from scratch.
Hopefully that all made sense. I do want to say that it's awesome you wanted to improve your frogs' environment. It just looks like you were mislead a bit along the way.
This is what I would recommend:
-If you can, pick up Tetra SafeStart (formally known as Bio-Spira). It's a product that literally contains the beneficial bacteria you need. You can pour it directly into the tank or onto the filter pad (I do the latter) to cycle your aquarium almost instantly. Most aquariums will cycle overnight with it (but test your water in case of a bad batch). Don't settle for any other product, no matter how similar it sounds. PetsMart WILL try to substitute something else if they don't have it.
-Test the water daily and keep track of your ammonia, nitrite, and nitrate levels. You want chemical drip tests, not strips.
-Perform frequent small water changes (remember to vacuum the gravel, if you have any) but leave the filter alone. 5% twice a week would be fine. If you get a bad ammonia spike, you can change more (no more than 10% for the time being).
-Read up on the nitrogen cycle. You can start here: http://www.paw-talk.net/forums/f77/c...ium-43789.html
-Don't add any more animals to the tank. This includes the "algae eaters" pet stores may try to sell you. I would, however, add some hardy live plants such as java ferns. They'll soak up ammonia and help speed things along. PetsMart stocks java ferns regularly. You can tie them to rocks, leave them floating, etc. They're pretty adaptable! The only thing they don't like is to have their "roots" totally buried.
Good luck and please keep us updated! Don't be hard on yourself, either, it sounds like you care about your frogs and are doing your best. Sadly, pet stores just want to make sales