Advice for my Pig that’s Very Prone to Bladder Stones

Hello! My pig has already had a really big stone and had it surgically removed. About six months later he has another one despite getting potassium citrate everyday. He’s now on a higher dose (0.75 ml twice a day) as well as another medication that’s purpose is to make him pee. I don’t know how to spell it lol

His current diet is:

Orchard hay 24/7

Romaine (everyday)

Bell peppers (all colors - 7-5 times a week)

Cherry tomatoes (2-4 times a week)

Cucumber (2-5 times a week)

Zucchini (2-5 times a week)

Yellow squash (2-5 times a week)

Oxbow organic pellets (every morning)

filtered water 24/7 (recently switched frim tap in hopes that maybe our water is just high in calcium)

What do you guys do for your pigs that are prone? I’m really at a loss and very stressed because I took out a loan for his surgery already and I’m really scared because that’s so much stress on such a little animal.

Any and all advice or resources is appreciated