Ammonia smell in rabbit urine - seems excessive? :(

Hi all,
I was doing bunny laundry this morning (Mimzy lives on cotton towels since he cannot manage a litterbox with his bad hips) and was blown back by how strong the smell was of the spots he's wee'd on his towels. Normally, the smell of bunny urine is not too bad, even if I've not been able to get the the towels for a day, but this was just overnight and it was worse than the cat's litterbox can get at times. I am a bit concerned.
Mimzy is eating orchard grass and western timothy, Oxbow brand, and their line of supplements; joint, digestive, skin and coat, immune support and urinary health. He also has a small amount of kale (not even the palm of my hand sized) twice a day to eat with his metacam (0.5 mls twice a day). The only thing he's been given in the last few days that's different than usual is a small bit of mint and an Oxbow treat cookie once a day that has a strawberry/banana component. He seems to be drinking water well too.
None of these things are anything he hasn't had before, but I was distressed by the level of ammonia smell in his blankets. I just want to be sure that nothing untoward is going on. Obviously he's been on metacam for years so this could indicate a kidney issue, but now that I am cleaning out the other two, I think their urine smells a bit strong also, though not to the level of Mimzy's.
Does ammonia fluctuate wildly like this normally? I had it explained to me once about the ratio of nitrates being involved, but I just want to be certain it has no connection to illness.
Many thankies for any and all replies. xxxx

If the smell is unusually pungent it might indicate a problem, but it is impossible to say for certain. Is Mimz maintaining his weight ?
Sometimes a bacterial infection in the bladder can make the urine smell a lot more, as can dehydration, some dietary supplements and of course it can occur in cases of kidney problems.

Sorry I cant give a more specific answer, as Mimz is OK within himself I would just monitor the situation and if the strong smelling urine continues to be an issue then a Vet consult would be needed. Sending vibes that this wont be necessary xx

Thank you, Jane. I'll keep an eye (and a nostril) on the situation.
He does seem okay within himself. I do think his pain relief could be raised though. We're starting to get cooler here and he is apparently feeling the chill in the air, poor bub. I can sympathize, my bones really ache and getting out of bed in the morning is a real task.
I hope you are feeling okay. I've been thinking about you and sending healing vibes your way. xxxxxxx