7.2 vs 6.5 vs 5.8 aren’t slight differences. +/- 2-3 tenths are slight differences but getting near the borderline of too much. Some strains won’t even tolerate that much without hermieing. The whole survive vs thrive ordeal.
Looking good is subjective. The ideal nuetral target of 6.8-7.2 for a balanced aquaponic system isn’t favorable to acidic plants, it’s just how life is. Transplanting into straight hydroton is obviously going to be very rough on the roots and will continue to damage them anytime they shift due to the weight and abrasiveness until the root mass takes over. That plant was already showing stress before the move.
It’s possible the hydroton hasn’t yet been populated with all the beneficial enzymes and bacteria the plant needs to feed it and since it can’t feed itself due to the high ph, its recovery is being hindered. And that once it does get fully populated within the hydroton and root system with the required bacteria it will return to the “looking good” state in the photo.
The question becomes, will the plant survive long enough for the bacteria to save it? Or are you willing to employ alternative methods? If it was I plant I thought was worth saving, I’d chuck the whole bag in a hempy bucket, flush it a few times, buffer ph to 6 and give it a handful of osmocote.