Well to your point of all the things that you did when your pH dropped, you did created a lot variables. It's very possible that one only out of the three of those variables you created maybe the main point that's causes the pH to drop or even something that you haven't tried. I would always recommend to do the process of elimination and find what factor helps your pH the most. You may find out that you don't need media at all. I my case, I could not for the life of me get my pH above 7.8, tested it with multiple test kits, made sure that Mag, Cal, Alk was all in range. I'm very certain that running media would have helped my pH if I would have went that direction. But, the moment I ran and airline connected to the skimmer outside, BAM!, my probe peaked at 8.36, recently calibrated and also confirmed with two different test kits.
The point I'm trying to make is that in this hobby we tend to over think water chemistry and we forget about the basics on what pH is and what effects it. The same could be said with any other target element we are trying to reach. If you find out what is actually causes the low pH, you can fix it. I will say that I am mostly against using any type of media in our aquariums, mostly because of added cost and maintenance, but also because, every time I've used media, it will fix one problem and cause another. I see media as a band aid for most problems and not correcting the root cause.
For example: Suppose an aquarist starts using reborn and gets the target pH they want, but then a problem of phosphates start to increase. Then that person that uses media start using GFO. Then what is the effect of using GFO? It seems like a cycle starts to happen and then you have some crazy conspiracy theorist pop up and starts to blame the big reefing markets like BRS making up scheme to take all our hard earned dollars spending on media just to enjoy the reefs we love!
Sorry had to add a little bit of humor in this post, it was getting to serious.
Love to continue the discussion.