@Al Mollet,
OK. Chlorine can break down resin over the years and it can become small enough to pass through under pressure.
Has your water pressure gotten stronger or weaker?
Two things that should be checked:
Shut off tabs for the brine and drain - check and replace as needed.
If that does not fix the problem you will need to check the basket on the bottom of the riser pipe.
Cracks will allow resin to escape.
How much resin do you think has escaped so far?