I've seen them in at least 2 spots not shown here (no screenshots unfortunately, bit hard to find evidence of them in a specific spot since there are so many)

Underneath the chipped edge of the lower part of the broken castle bridge (Ancient forest)
Screen Shot 2020-02-04 at 3.50.09 pm

No actual frog in this one but that's where they spawn

Under a tree
Screen Shot 2020-02-04 at 3.56.06 pm
leaf between the two listed tree spots in the Pits, near the staircase-looking stack of rocks 
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