I dont know how long youve had your 30 set up, but it seems as if your adding fish a little fast as well. Coral Beauty and batfish the same day, the adding a blenny the next? Take a couple weeks between fish to let your bioload keep up, also angelfish need a tank thats established, been up for 6 months or more, good luck with your fish, but seems to me that there was more mistakes here then just the batfish.