Hail folks. So today was a horrible day, I woke up to a dead frog. I bought the frog at Petco on Monday, and I noticed last night it was much thinner than its partner, and seemed disinterested in food (also purchased on Monday). This morning it was stiff and sprawled, and not breathing. It occurs to me I should have taken a photo, but in my distraught-ness I did not. At any rate they did replace the frog for me, but I have no idea why it spontaneously died, and I'm taking no chances. Both frogs are being removed from the tank, and put into separate quarantine boxes, upon completion of tree bark sterilization, which is ongoing. Questions as follows...

Firstly why did my frog die?

Possible theories:

The peat moss I had in the bottom of the tank was Miracle Grow brand, and was probably laced with fertilizer. I feel it is possible this may have contributed to the decline of the frog, does anyone know this to be true?

I had several pieces of tree bark that had been hot glued to the sides of the tank. This is fairly common practice for tarantula enclosures, but I found one of the frogs partially wrapped in a hot glue "stringer". I of course panicked, unwrapped the frog, and removed all of the bark. One of the frogs was dead two days later, I am uncertain if it was the one who was wrapped in the stringer. Is it possible the frog was impacted with a hot glue string?

The tank had a layer of native moss on the bottom, which had some pine needles in it. I'm wondering if the pine had some sort of terpenes in it, or if the frog accidentally ingested one and got injured.

And lastly it is possible it was just a sick frog, from a crowded tank in a pet store. I should mention the other frogs (the replacement and the old one) are both acting normal, one molted tonight, I'm not sure which one...

Secondly are my quarantine tanks acceptable?

The rigs I am building now, are simple plastic bins, each one is 4.1 gallons. Is that too small for a 2.5 inch nose to vent frog for temporary quarters? I will be drilling holes in the lid, or cutting a large hole and screening it in, when I get a dremmel wheel probably on Monday. I'm not sure what to do for heating right now, I have a single ceramic heat lamp, and a single "rainforest" UVB CFL, it will be difficult to do both tanks with those, I can buy more stuff if necessary. For a "water bowl" I have a shallow (1/2 inch deep about 6 inches long 4 inches wide) leaf shaped dish, it is labeled as microwave and dishwasher safe, which I assume means it is intended for serving food, so I assume it will be Ok for a water bowl. I guess I'll be using paper towels for substrate until I find a proper solution...

So thirdly... I'm ready for a scolding...

Is there anything else I need to know, any red flags jumping out? What did I do wrong, what did I miss? I do not want to lose another buddy...

Thanks in advance guys...