Its nowhere else i checked. I was using newspaper and carefresh on top level and lino on bottom with some hay in their beds. But have just switched today to newspaper puppy pads and hay ob top level and still lino on bottom level.
Blood has a different specific weight to urine. If there are significant amounts in the urine, it either dries as reddish dots in the middle of a normally coloured urine stain or - if there is more - as a reddish ring around a differently coloured urine patch.
It is very likely that the brown cardboard is distorting the colours and - as you cannot find any more evidence of bleeding/bloody urine - that this is simply an oxidised urine patch. These tend to dry a dark rusty colour in contact with air the older they get.
Have you checked the pigs over for any obvious signs of injury? Try brushing their fur against it's normal flow. Whilst the marks may or may not be blood you need to make sure that there is no obvious injury to your pets. How long have your girls been together? Mine had been together about 6 weeks but two of them decided not to get along this week which resulted in blood being drawn, a couple of the wounds where very difficult to find hence why I have suggested brushing the hair in the wrong direction (though all my pigs hate having this done)
Sorry for the delay my phone died and thanks for the response. Theyre 5month old sisters so i presume they've always been together. Will try and hold Fudge after to check her but its not easy they really hate to be picked up. I held Smudge yesterday and she was fine so just need to check Fudge.
Just had a thought as i was giving girls their nightly pile of hay...on Wednesday i bought timothy hay with dandelion and marigold for the first time and was wondering if the orange marigolds had changed their wee colour maybe?