Thank you so much for all your suggestions & well wishes, we appreciate it so much!
I've been reading more & found this, I feel absolutely sick that I made him sick.
THK is mainly plant proteins. I wouldn't be surprised if it's his diet, hoping it's not an infection & a change in diet will help him.:
An increased amount of ammonia in the urine causes the formation of struvite crystals. This increase can be caused by bacteria from a urinary tract infection or from a diet consisting of mainly plant proteins.