@Eohsi_ I’d disagree, you are still kinda new to the gym so doing compound lifts would benefit you more than isolation movements due to it working multiple muscle groups at a time. This will allow you to build more muscle mass for now at a faster rate. Isolation work is still good tho.
@Eohsi_ Yeah it’s most likely because they haven’t recovered. Change ur split so you have at least 2 rest days and make sure in your split you aren’t training the same muscle group 2 days in a row etc