My mare is odd about her pregnancys...what about yours?

I had an old mare that I tried for 5 years to get her in foal, she was a red dun quarter horse, at 20 years old we finally got her to take, she was only bred one time due to an accident with the Stallion owners Grandson, but she took, 372 days later she dropped a beautiful healthy Sorrel and white filly. She carried her over a year and boy was I nervous, she was 21 when that filly was born and it was her last foal, she died at 30 years old.13 years later that sorrel and white filly had her first foal, she was bred to a big black and white stallion he was 16.1h and weighed 1350 lbs.it was a colt she carried it 354 days and he was big sorrel and white, beautiful colt. that was 2 years ago I had a heart attack so I sold my mare and colt last year.