Calcified Tumor

Hi all, Im new to this forum and wanted to ask a couple of questions regarding one of my budgies. I have a large aviary with numerous birds in it, plus 10 budgies. At the begginning of March I found a little girl on the ground of the aviary. On further invesigation found she had one of her eyes bulging out and bloody.I have more birds on the back verandah in numerous cages which is used as a bird hospital. Anyway as i live in the country and getting to a vet not always convenient I bathed her eye in epsom salt and applied certigen(purple spray) to it twice a day and kept her isolated in her own cage. She recovered but lost the eye. Anyway she went through a period of depression, running around in circles and sitting in a corner. I introduced Jo Jo a hand reared male to her and they are now a pair and she is a lot brighter and happy. She is also a beautiful natured little girl, has never bitten me and could fly but can be handled and has never attempted to fly off. Anyway... Im getting there.LOL she has been laying eggs, very brittle shelled eggs and I was giving her a scratch and noticed a lump near her opening. Thinking she maybe egg bound and as I was travelling to Perth that day I took her to the vet. He operated and said it was a calcified tumor. Removed it, stitched it and gave her a slow release antibiotic. Can anyone on here tell me anymore about these type of tumors? And perhaps how they are caused. And perhaps how she got the injury to her eye. She is the sweetest little girl and really pulls at my heart strings, not the preetiest budgie around but lovely. Thank you in advance. Cath