Why did my dogs get fatally sick and pass within weeks of each other?

[Momoffurbabies]

My 7 year old German Shepherd first showed signs of being sick. She was having some issues with her hips so we did an xray that showed no obvious hip dysplasia. She was given a steroid shot and sent home. The next day we woke up to find she had urinated herself in the middle of the night. It was bright orange. We called the ER vet and were instructed to bring her in. We discovered her ALT & AST levels were over 1,200. She was diagnosed with Lyme disease and hepatitis (she likely got the hepatitis from the Lyme disease?) She was hospitalized for 24 hours, given fluids and lots of medicine. We were instructes to visit our vet in a couple days to recheck her levels. At recheck they were 500 and 800. We were then instructed to bring her back 2 weeks after she had finished her medication. Before the 2 weeks was even up she started showing symptoms of being very sick (laying around,lethargy, urinaying herself, orange per, anorexia, increased thirst, etc). We rushed her into the vet and once again her levels were well over 1,200. We were informed she likely had a tumor encompassing her liver that was stopping it from fully healing (she was given an ultrasound and it showed a very enlarged liver). We were told we could give her some meds to make her more comfortable and keep her around longer but her liver would likely never heal fully. We made the difficult decision to put her down.
In the time frame our GSD got sick our Boxer mix also staryed getting sick. 2 weeks after our GSD was brought to the ER vet our Boxer had a seizure (her first one ever). We were instructed to monitor any events for 2 weeks and bring her in, as 1 seizure in 6 years is not a major cause for concern, and we were dealing with a very sick other dog. Within those 2 weeks she had 1 other seizure. We were told she likely had epilepsy but personally it would be best to wait on medication unless it got worse because she would have to be on it for the rest of her life. She went several weeks with no seizures. 2 weeks after our GSD passed she had 2 in the same day. We called and made an appt with the vet to get her on meds. Our appt was for rhe next week as it was a holiday weekend. 2 days later she woke up urinating herself. Again, we rushed her to the ER vet. Her blood panel was normal, the only cause for concern was concentrated urine and a slight UTI. She was given Amoxicillin. The next morning she woke up and was acting strange, walking in circles and being extra cuddly. We were given anti seizure meds as they suspected there may be some sort of misfire in the brain. The next day she started bumping into stuff and becoming extremely lethargic. We were instructed by the ER vet to get her an MRI ASAP. The only ER vet that did this on holidays was far away and I was 38 weeks pregnant and could not travel. The next morning (12 hours later) we rushed her to our vet and were told she was blind and had signs of a mass causing pressure on the brain. We put her under 24 hour observation at the vet where they medicated her and she did excellent during those 24 hours. The next day as they started to wean her off the medication she had a massive seizure and passed.
What could have caused both my dogs to get so sick in such a short period of time? Both extremely different symptoms, but both fatal. Losing both of them within 3 weeks of each other and being extremely pregnant is worrying me it could have been environmental, though our water has been tested and came back clean (the only test we are still waiting on is arsenic).