I've found out what they are.It's best when having a question like this, to turn off your texture/resource pack. That way in the default we can accurately determine what's going on
I've found out what they are.
I ran into a Tainted biome and a Tainted Swarm attacked me and it looked exactly like this. However the ones in the screenshot are not the actual mob and just seem to be a visual glitch; my friend reported having seen the same random lights after encountering a swarm. I'm going to be reporting this as a bug.
Thanks for all the help guys and sorry for the op, it was kind of late.