It should absorb phosphates, but I am not 100% on that specific product. Realistically, I am thinking they may be coming from your other filter media. Try replacing them when you do PWCs and see if that helps. I am also unsure on the capabilities of the Pura pads.
I was recommended the PURA pads by a moderator on here, so I went with the recommendation Also, PURA recommend changing every 6+ weeks I believe, but I change them every 4. I can try changing them every 2 weeks though, if you think that might make a difference. I could put the Rowaphos sponge at the end of the PURA pads maybe in my filter?
Maybe I missed it but have you tested your PWC water to see if you are adding it to your tank.
Yeah, I've tested my RO water and nitrates/phosphates were undetectable again.