Holy **** in the 3000 page book you wrote, I completely missed that!! YES!! You most likely have them in backwards!!!
"How do you tell" I don't know, they may or may not be marked. You CAN determine the PC board, all you have to do is LOOK. The positive side EG the TS indicators, has a trace going from each socket directly to on cluster connector pin. So does the high beam
You cannot damage an LED with wrong polarity. They simply won't work