Something like 12 years ago I participated in tournaments for fighting. After many years I learned that one can get killed by getting hit in the liver area and so on... I don't know if this depression or overthinking thing has ever made you suffer or not so I want to know if my hopping side kicks to the opponents has done them damage. I was 57 kilogram and highly trained with great flexibility. In one occasion I knocked down a karate artist who had a black belt by kicking around right part of belly and the other time I threw a hopping side kick to my opponent but he wasn't knocked down and he decided not to continue the fight after it.
Lots of people fight full contact (muay thai, kickboxing, and full-contact karate systems like kyokushin) for years and take blows like this regularly - if the guys got up at the time and seemed ok, the chances that your blows had any significant long-term effect is incredibly small. That one of the guys was still standing suggests you didn't get a particularly solid liver shot in that time anyway. How badly they'll have been effected depends a lot on whether the attack caught them unprepared - with muscles relaxed, especially when inhaling - the attack can more easily penetrate to compress the liver. You were light weight, and - no offence intended but in my experience - that you mentioned flexibility as if it was of any real significance suggests you don't understand body mechanics terribly well, which means you've probably never employed them terribly well, so just more reasons to think the strike was unlikely to have had a lasting effect.