hey 👋
I don't see your grow log, but I assume it's a photoperiod plant?
If so, your plant went into re-veg because of an issue with the light cycle.
Genetic instability is also possible, or a combination of both
think virus is a possibility too... but can't be certain about any of it just looking at it. not worth sending a sample to a lab, either.
at this point, if it was communicable, it would have spread, so no harm.