This may only happen in the initial break-in period of the skimmer. Once the skimmer has break-in, minimal micro bubbles should escape from the skimmer outlet.
From your picture, dun look like melt off but instead pest invasion. My advice is take out all your zoas and dip with coral RX or TLF ReVive Coral Cleaner immediately.
Good thing never come cheap...hahaha..! For your budget, you either stick back to what your current lighting or buy very old or obsolete good LED lightest which has some risk that might have no spare part replacement if breakdown hor.
Why not consider SKIMZ DC Protein Skimmer D-series SM163? Price wise slightly higher than SM161 nia.
IMHO, SM161 is a very good and effective skimmer with solid built which able to skim out a lot of dry brown skimmate for my previous 3x2x2ft tank.