Two Fire-Bellied Toads dead after only 4 weeks?

[SB]

So I bought two fire bellies toads about 4-5 weeks ago, and then I looked in the tank yesterday night and one of them was dead. He had eaten earlier that morning and everything seemed fine. The other one turned a darker brown (which I thought was due to stress). In case something was wrong with the water or enclosure, I took the second frog out and put him in a transport container with fresh water for the night. When I woke up in the morning he was dead as well. When I first got the pair they instantly turned brown in the enclosure and stayed like that until I purchased a light and rearranged the tank to allow more sunlight in. They turned brighter green again and everything seemed perfectly fine. Other than noticing some bubbles on the water occasionally, everything seemed normal since they were eating and pooping regularly. I was hoping someone had any suggestions of what might have happened? I love FBT’s and would love to get another pair but I don’t want to get them before I resolve this issue since this devastated me. Below is a bunch of information regarding my situation to help understand better (found on a separate forum). And suggestions are appreciated. Thanks


1----what 'kind' of frog is it ( what species)
Fire Bellied Toad(s)
2----please include a photo of the frog

3----Please include a photo of the frog's current enclosure
(The deco pieces had been moved around about after this photo was taken but all pieces remained the same)


4----size of enclosure ( W" x D" x H" )
12X12X11


5----# on inhabitants - ( if there is another frog --- is there a size difference ? )
There were two, one was a little bigger than the other but not by much


6----has or was the frog kept with a different species or with any other tank mate
They were purchased together by a reputable pet store (not a chain)


8----what is the typical humidity level
70-80


9----what temperature is maintained
70 degrees F both air and water


10---what is, specifically, being used to maintain the temperature of the enclosure
I had the enclosure set up for a week and a half before I purchased the toads, and it maintained the recommended temperature the entire time so nothing was used


11---describe the enclosure lighting ( very specifically)
A lamp hanging over the tank with a 5W bulb inside on a timer to simulate sunlight


12---describe enclosure maintenance ( water changes, cleaning etc)
Filter was used to maintain water clarity, water was changed every two weeks and excess crickets (dead) were scooped out of the tank regularly


13---what kind of water is used
Tap water with de-chlorinator (brand API)


14---material(s) used for substrate - be very specific
Medium river rocks (bigger than the toads head) was used


15---enclosure set up:
Enclosure was rinsed down with really hot water and scrubbed with a new clean sponge, plants are flexible plastic cleaned the same with hot water and the sponge


16---when is the last time the frog ate
The morning they died (about 8-10 hours before)


17---have you found poop lately
Yes


18---how often is the frog fed
Daily


19---what size feeder is given
Large crickets (they ate 1-2 crickets daily)


20---what other feeders are used as treats
Tried freeze dried mealworms but the toads were not a fan (didn’t eat any of them) and I didn’t have time to try anything else before they died


21---what is the frog's main food source
Crickets


22---do feeders roam free in the enclosure or is the frog bowl fed
Roam free


23---vitamins - what brand and how often
None


24---calcium - what brand and how often
Crickets were sprinkled with calcium about once a week (Flukers brand)


25---was the frog without calcium for any period of time
Most likely during the periods not sprinkled


26---approximate age of the frog
Unknown


27---how long have you owned the frog
4 weeks


28---who cared for the frog before you
Bought it from store


29---is the frog wild caught or captive bred
Unknown


30---how often the frog is handled -- are gloves used ( what kind of gloves)
Only to take out of enclosure for cleaning


31---is the enclosure kept in a high or low traffic area
Low


30---has or was the frog properly quarantined (yes or no)
They were placed in a new tank together so no quarantine took place




32---has the frog been treated with any medication:
No