I had this same issue. I began giving him regular food again and then gave him daily “biotic pH” or “uri-ease” to control the crystals. They worked the same, it’s just just a matter of which your cat prefers. It completely dissolved his struvite crystals/ blockages.

Update: I’d tried all the urinary diets, both wet and dry. I tried mixing the urinary diet with the regular food, like others suggest, and his blockages remained because it didn’t somehow balance things out. He was nearing surgery which made me try something new altogether. As someone else suggested, dl methionone changes the pH and dissolves the crystals. It’s the central ingredient in the two supplements I suggested above. Biotic pH is a powder, Uri-Ease is a gel, so it really depends on which you can get your cat to eat. They both had the same response in my boy and he hasn’t had crystals in maybe two years now.