It was misty lower down but reasonably clear higher up but you could be right, I shot quite few yesterday morning but this was the only one from that location in that direction and the sun is to camera left.Mist and low light? Rainbow effect?
This was LR Auto adjust and then dehaze to illustrate the problem, no HSL, no polariser.Is dehaze the only setting used here? I know HSL can cause some very odd artefacts as well. Or was a polariser used?
The exposure was pretty good, I noticed it when I pulled the highlights down a little but it was nowhere near as exaggerated as this.Was it over exposed? If so then you peg the highlights these sort of things can appear.