pacman turning brown?

[SiNi5T3R]

Well I have the same substrate in my bullfrog tank and one of my toads has also started turning the brown coloring on his back. Im starting to think its the tannins from the substrate leaking into there water portion of there tank and its just turning there skin a off coloration. As far as I know tannins are harmless to reptiles. Its okay for frogs right?

[BG]

Before I was looking for a pacman frog I did some research and I found out that the green pacmans loose that bright green when they are babies so what I did was I picked one up that had very few spots a on him but to tell you the truth there are brown ones from the fervor so the green ones are not really a try brown color its a different tone of colors that's why I love these guys they have the coolest patterns even the real brown ones.I THINK IN THE WILD THE LESS SPOTED ONES WOULD OF GOT EATIN BECAUSE THE MORE SPOTS YOU HAVE THE MORE YOU BLEND IN BUT THE PACMAN FROG IS A SMART ANIMAL IT HAS LEARNED TO ADAPT LIKE MY FROG CHANGED FROM SOLID GREEN TO A MULTI COLOR PATTERN

[Tree Frog]

It may be because of tannins but i didnt think they affected frogs