Help figuring out how to help our little man.

Hi there friends! My partner and I are concerned for our little guy and are hoping for some insight and recommendations. We thought his harness might be causing these issues on his chest/sides, so we got him a new one. My partner looked into recommended harnesses, and got one for him based on that (Ruffwear harness). We’ve been using the new one for a few days now, and he still seems to be having the same irritation. We loosened the harness and it’s still causing issues and honestly looks worse. He goes to daycare on our longer work days for anywhere from 8-10 hours, and while there has to wear his harness the entire time. Are we correct and this is likely a result of his harness? Is there a better harness we could get for him? Is there anything else this could be and if so, recommendations on how to help? It doesn’t seem to be bothering him, at least. He doesn’t notice it and we can touch it and he doesn’t mind. It just looks rough to us and we don’t want him to be uncomfortable. Thank you in advance!