That does not sound too bad, perhaps try and get the ph down a teeny bit but 7.4 is not seriously high to cause death. They do specify they are omnivores so perhaps give a bit more bloodworm and brineshrimp. I have the exact same tank, its a lovely tank. Maybe do two 20% waterchanges this week just to make sure you get all uneaten food and stuff out. I only have teeny fish in my tank so not sure about whether you are overstocked or not, does not sound like it, but I am also new in the hobby. For your ph problem try aragonite that is what I have in my tank to stabilize my ph.