I've never kept SD's but I believe they can be extremely twitchy. Have you any decor that they could have injured themselves on during a sudden burst of speed?
Also, do you think your plecos could have something to do with it? I ask because your tank seems very busy, if the plecos aren't getting their share of food, if they're very hungry, and dependant on what type they are, they have been known to attach themselves to fish.
It's a long shot but if you can rule it out then at least you're closer to finding an answer.
Also, do you think your plecos could have something to do with it? I ask because your tank seems very busy, if the plecos aren't getting their share of food, if they're very hungry, and dependant on what type they are, they have been known to attach themselves to fish.
It's a long shot but if you can rule it out then at least you're closer to finding an answer.