JD, welcome to TFP!
Well, as you have now learned PoolRx is 30-45% copper sulfate as seen on their
SDS. That copper isn't going anywhere unless you change the water, and I highly doubt you will have success trying to filter any of it out. You can try the acks Magic Stain removal program which I believe uses the Blue Stuff (maybe magenta) Copper and Scale remover, but then a water exchange will still be necessary. PoolRx is a pool industry gimmick and not a substitute for proper sanitation and/or algae removal. Only chlorine will do that. But here's the real problem.
Before you do anything else other than add liquid chlorine, post a full set of water test results from your TF-100 or Taylor K-2006C test kit. We need to see all those numbers. If you don't have one of those kits, STOP and order one ASAP. I recommend the TF-100 (link in my signature). It's a must and we need to see those accurate results first.
Based on previous pool chemistry care, I have a concern you may already have algae, or at least algae-related staining (maybe calcium staining) which can embed in the plaster as well. You should also be aware that some copper treatments can really skew your free chlorine readings which can throw-off FC testing as well. So there are several things to consider in your situation.
Finally, while this may not be the ideal time to do a water exchange, you could consider an overnight water exchange. At dusk, get yourself a strong sump pump which will suck water out rather quickly, then refill. It would be ideal to get most of it changed, but even if you only made it half to 3/4 of an exchange, it may be enough to reduce your copper levels before the mid-day sun and UV kit. But let's start with some accurate test results and we'll get you going in the right direction.