cory with no barbells

i picked up some julii cory’s about a month ago, most of them are doing great, but one looks like it has shortened barbells, is lighter then the others, and has redder gills. other then that his behaviour is normal and he is eating great. i had fine gravel when i first got them, and switched to fine sand as seen in the video. i feed them sinking wafers, blood worms, shrimp pellets, and whatever baby brine shrimp or bug bites make it past the rest of the fish. tank ph is 7, trying to get it a bit lower with almond leaves right now, 76 degrees bc juliis like it a bit colder, and i do maintenance and water changes every 4-5 days to keep the beach clean for them. should i be worried? should i quarantine him? will they grow back? also, they share the tank with embers, green neons, clown killifish, shrimp, snails, and freshwater bumblebee goby’s that ive had for 7 years and are extremely friendly.