Ditto Trinity & Kayella. They're 'growth' or 'founder' rings, that would have started at the coronary border. Perhaps you didn't notice them then because they look minor & periople may have been covering them until recently.
I think it's important to recognise & consider what is now termed 'low grade' or 'sub clinical' laminitic signs such as these. As Trinity says, no cause for worry, but something to be alert to. If you can recognise & consider the minor signs like this, I believe that the vast majority of major 'founder' can be completely avoided. 'Sub clinical' means no clinical symptoms, such as pain, lameness, inflammation, so many people don't even notice it, let alone recognise it as a laminitic 'event'. Laminitis can be caused from all sorts of things aside from diet/obesity. Any serious stress, physical or mental can potentially cause problems. They can be a short term, 'one off' type minor event, such as it seems this eg is, or they can be ongoing or major, causing constant rings & distortion that goes with that, or a major breakdown.