Often eels do tolerate one another for their one most aggressive behavior comes from feeding for as even eels like the goldentail moray, one could house a pair for so many years and one day one took some bites out of the other. That happens even more when house different growth eel species.
As it is, you seem to have species which would mostly feeds mainly on crustaceans. Now I cannot see the photos as clearly, but few the eels I think I make out a Sharptail in #1. I see where you say that the biggest eel is 10" or so.
Which the eels you had for 3 years and what size were they when you first got them? The enigmatic eel will grow less then 2' and would feed on small fish as well the White ribbon eel will grow more then 3' and from the photos you show, it and the enigmatic eel are your most active from the bunch.
The white ribbon likes to burrows itself for its protection and when small size do feed on crustaceans such as shrimps and soft shelled crabs and can be difficult to feed in a home aquarium, especially when too small a juvenile for feeding it only one type of foods is not a good thing.
Now is it my eyes that im seeing a yellowish color in your tank?
Just how often you do water changes and how many gals?
Now understand, I for many eels kept eels and for some 37 years or so, I keep all that time seven eels at any one time, but only my tanks were larger for when the eels become adults, there could be problems being in a tank that is less then 3' long, even three feet for that matter.
Eels always show at most their docile appearances and their reasons to bites other eels in the tank happens due to two main reasons such as hungry and their lair. For yes, this can appear to work well for some years, but one day you will remember what I said here for even dwarf eels bite another of their kind due too their normal aggressive behavior.
So right now that the eels are so small, you no issues as yet, also your a wide mix and thanks god for one thing that your not other species of eels, which feeds mostly on FO.
So yes, its an interesting collection of eels.
If you were to add a wolf eel, you see bites taking out of the other eels real quick like>
Also, I cannot tell on how much LR you have there, but eels like to hide themselves completely and in total darkness.
You might to tell what filtration system your using on these tanks? And how much LR?
Also when I housed three or four eels together of a difference species and depending on their types of behavior for the long term, I housed them in much larger tanks in order to keep any aggression to a minimum, but there are no guarantees.