What are the water parameters?
Ammonia
NitrIte
Nitrate
What is your water changing schedule?
And are you familiar with the nitrification cycle? It basically is where Beneficial Bacteria aka BB grows in the filter and helps process ammonia (with is bad for fish) and waste into not toxic water.
The info is in my signature and explains lots of pertinent info for tank keeping, very useful article.
Test the water and record the results.
I would do 2 - 25% pwc one right after the other. Then test the water again.
If you do not have a test kit or can't get to a store which can test the water, then after about 4-8 hours do another pwc 25% and then another after 4-8 hrs. These gradual water changes help the frog get used to the new very different water quality.
If the situation is very very bad looking for the frogs you could shorten the time in between by say 1-2 hours after the initial 2 back to back changes.
If you get the water tested then you will know - record the numbers for each thing, ask for the specific numbers they get, not just an answer of it's okay, or a little high, etc.
Then you will know 50% change of water is going to reduce the amount of the danger zone parameter by about half. It doesn't exactly end up as half if you do 2 25% water changes because you are changing parts of the amount mixed in with the current water, not just a straight remove half of the water. and also why it might take more water changing to get a better /safe number.
If you get a kit from a big box store they will usually price match the cost of the master test kit with themselves online price (often less money online) or their near competitor. You can ask them when they price match with and look it up so you know.
Try and make sure the water is temperature matched and dechlorinated. de- chloramine if you have those in your areas water.
Also ADF are supposed to be rounder than they are usually seen when sold at the stores. Rounded because of healthy eating though, but not bloat because of illness / poor water quality.
