Most units have proprietary threads. I went 6 years taping the ends of mine and getting lots of ouchy drip splatters. When I finally broke down and looked up the caps they were $17 and I kicked myself. Hard.
I have to ask tho. You have visible buildup, right ? Toothapaste or Chalk ? The plates are pretty dull grey and won’t ever be ‘shiny’.
If you do need to clean with acid use a popsicle stick to knock off as much as you can between the fins. Then give it a bath only until the fizzing stops.