Michaela,
As this started in march as the temperature start to rise this could be a simple heat rash. I don't know what your weather has been like this year but the UK had one of the warmest starts which was a huge help in lockdown as everyone was able to spend time in their gardens as opposed to being cooped up indoors. It did mean however warn nights and I noticed that I sweated a lot more under my forms during the night.
