Think it was his poop it was hanging on him from the bottom of his body but as far as feeding i Feed frozen brine n mysis shrimp I add selcon 2 it let it soak before I feed them I stopped with the selcon and started using garlic
What you're feeding it isn't right, you need to get more greens and algae into its diet. Things like Spiralina Flakes, Formula Two Flakes and Pellets and Nori sheets is what it needs, not brine shrimp or Mysis.
There's a frozen flat pack which requires overnight shipping or there's a refrigerated liquid caviar version which only requires 2-day shipping ($7.99 @ Premium Aquatics) if no LFS has it.
Maybe call a few LFS in the Bronx to see if they carry.