Pressure washers are fine and will do no harm, but they have to be used properly. Specifically this refers to the distance the wand is held from the surface being cleaned. Too close and damage is imminent.
That being said, it is possible there was a problem with the grill, with all the cost cutting measures used lately. In any case, a good way to remove
from the grill is to soften them first with a diluted solution of household washing ammonia. Spray some on and keep the grill wet with the solution for at least five minutes. After this the
will come off with minimal pressure.