No, they not need to be feed on the daily basis and if you do this, it leads to problems down the road and because you have the four eels together is why i say that you do need to do water changes once a week. You need to trust me on this
How big are your fimbriated morays right now? And you need to feed an variety as possible of foods and you not need to feed any more then one or two a types of foods at any one feeding period.
Like every third feeding, my dragons eat only octopus, this is to give you an idea of what i mean. And sometimes i feed only grouper at one feeding, but never do i feed just three kinds of foods only, they need a variety of foods. Now i never heard any eel lose its sight, but i did with puffer fishes and a number of other species and the reason for it is as i mentioned, a variety of nutritional foods with excellent water quality. If the fimbriates should grow faster then your SF, it could be in danger for the fimbriated will prey upon any smaller eel then itself when hungry, you need to know this for with the Jewel, you not will have this problem as a tank mate with the SF.
If you not believe me as of right this moment of the fimbriated mora eels aggression, then ask around.