Welcome to the forum
Piggies do have naturally milky urine and it isn’t always an issue. However Their urine is very alkaline and due to that it can leave them prone to bladder problems.
Does it leave white patches on bedding once the urine has dried? Do those patches feel powdery?
If so then that means they are excreting excess calcium in their urine. This is normal and ok to some extent but only if it happens very occasionally.
If it happens a lot or if the dried patches feel gritty when dried then it means their diet is out of balance (and that can be too high or too low in calcium - both are as bad as each other so it is about finding the right balance) and you need to look to make dietary adjustments.
These adjustments would take a while to have an effect on the body so it isn’t an immediate effect.
If it is gritty now, then you should see a vet and have them checked for sludge/crystals in the bladder.
Things to check:
- Ensure you keep pellets strictly limited to one tablespoon per pig per day.
Ideally you feed a pellet which is grain free and grass/Timothy based. Try to avoid pellets based in alfalfa (may also be listed as Lucerne)
- Filter their drinking water. I see you’re in the UK which is mainly hard water and water and pellets (which contain more calcium than the highest calcium veg) together contribute most calcium into the diet.
- keep an eye on what high calcium veg you are feeding and its frequency. You should avoid feeding high calcium veg more than once a week - items such as kale, spinach, parsley should be kept strictly limited.
If you could us details of their diet and any other information which you think may be relevant then we may be able to assist further.
There is a balance to be found and it can be different for everyone to find it.
For example, I don’t feed any pellets at all so it gives me leeway in the veg part of their diet and can feed higher calcium veg, they are also on grass a lot. This together means their water intake is higher so it keeps the bladder flushing through.
I have added some guides below which explain further
Wiebke's Guide to Pees and Stones
Long Term Balanced General And Special Needs Guinea Pig Diets