Aik, susah nak agak from your description je, especially since you say some fade and some get darker lepas few days, tu memang beda pattern dari mosquito bites biasa yang usually redden then fade. Kalau ada yang naik dekat kepala lagi, lebih baik jangan tahan-tahan, bawa dia jumpa doctor je untuk confirm, bukan trying to scare you, tapi better safe with rashes yang macam spread dalam seminggu and getting darker gitu. One of my mum friends' daughter had similar bintik yang slowly turned darker and it turned out something yang memang kena antifungal cream, so timing tu penting lah. Bila you perasan it's evolving like that, doc can do proper check yang satu dua minit je. Hopefully nothing serious, but lepas tengok doctor you boleh be more at ease kan.