Phrynomantis Microps skin discolouration, not sure about the cause.

I bought these two little guys from petshop where they claimed them to be Phrynomantis bifasciatus but later i confirmed them to be actually of Microps species, price was low and i took pity on them since they were in dry setup with almost 34 degree Celcius, both are very active in room temperature (23C) during nighttime and feeding well on baby crickets with some calcium powder (no phosphorus) im keeping them in high humidity in small paludarium.
One has standard colour for that species but...

Phrynomantis Microps skin discolouration, not sure about the cause.