When you come back, do try to see what happens if you completely stop feeding frozen foods.. fish can be picky #19###s sometimes, but a well fed Apisto in a planted tank can normally go for two weeks without food and not even show signs of it. Maybe your Apistos are well fed enough that they are just waiting for the frozen to come back onto the menu.. but don't take this experiment to the point where they start looking thin!
Could it be finrot induced by fighting when you are not watching? That would explain the splits as well.Okay, so a bit of an update: I don't think this was fin rot at all. His tail recovered in places and then just split in others, it got better for a long time but this last few days it's gotten worse again and I have no idea why. Water params are 0-0-10. Same tank inhabitants and haven't added any since. Today his tail went from having a couple of minor splits to having part of it completely split down the middle and I have no idea why, I feed him a mix of frozen bloodworm, frozen brineshrimp and frozen daphnia as he doesnt eat anything else is this an acceptable diet as I've read that it could be due to a vitamin deficiency?