Hi there in Oz! Nice to have more members from down under!
It might be something called urine scald. This is, as you might expect, from exposure to pee and is more common on the back feet because that's where the pee is! Have a careful think about your bedding situation because that's probably key here.
Urine scald on the back feet can be seen when piggy has urinary tract infection including symptoms of dripping pee but your pig looks fine - that photo shows a nice clean dry bottom end - and white pigs are always handy when checking for things like that as the colour doesn't let them hide anything!
Long-haired pigs can also get it as when they pee some gets soaked into the feathery back legs and dribbles down.
When I got my long-haired girl I got caught out with urine scald on her back feet... but only when I tried out a new type of bedding. There wasn't anything wrong with it but it was different to the old type. Bless her, she's a big fat girl and she loves to lie around eating, and she was peeing where she lay and it wasn't soaking up quite as fast. Just under a week later she'd got pink back feet - eek! I switched back to the old bedding and, just for a few days, I rinsed her feet in warm water and applied a tiny amount of barrier cream to the redness - I used Sudocreme which is a baby nappy cream here in the UK and not really recommended by the forum because over use can lead to thinning of the sensitive skin and when breaks start that's when you risk the open sores of bumblefoot. So it was a bit of a gamble but it prevented our problem getting worse - I also trimmed her bum and leg hair at that point and kept a close eye on her until her feet were a proper colour again!
Check out where your girl is sitting or lying most of the time and there is likely to be a big wet patch that is causing this problem. That will just have to be scooped/changed more frequently. Neither of your beddings are 'wrong' but you just have to manage them in different ways. Shavings have to be spot-cleaned daily - poss twice a day for pee if you're trying to get on top of a problem. For fleece, you might have to put smaller 'pee pads' on high use areas and switch them out daily (or the bits of towel underneath them at least). I use a fleece-zorb-fleece sandwich where the zorb is an absorbent fabric that soaks up the pee... but it's pretty lightweight so the pee spots will dry out overnight. When you have towel underneath it soaks up really well but stays wetter longer so the pressure of a pig lying on the fleece above it can cause pee to soak back up through the fleece. But you can cut towel up into bits and just have a bit that gets switched out every day so you're not always washing giant soaked bath sheets!
I'll finish with a pic of my rubbish sewing - I have a machine but you'll see here that I didn't do hems or turn things inside out neatly. I just stacked up the fleece, zorb and fleece and machined a square(ish) and then cut the extra bits off the edge. It does fine!
If she gets any worse it'll be a vet trip before bumbles set in. Try to nip this problem in the bud though because it's going to be cheaper. If you have another piggy companion (they should always have the company of other pigs x) compare the feet to check they don't have the same problem. Like I said it's handy having a white one with pink skin as they flag things up straight away... my darker pigs I have to get in a good light with my glasses on to see anything!
Good luck and keep us updated
