"Tangerine" probably Satsuma mandarin.
Grapefruit very likely to be Melogold or Oroblanco (more likely Oroblanco) because of the large size.
If the Satsuma mandarin tree is not that old, you may have to wait a few more years for the tree to improve in flavor.
It can also help to stop watering the tree right around the time that the growing fruits are sizing up.
Last year you may have waited too long to begin picking the fruits. Sometimes the fruits will be ready to eat before the skin on the outside has finished turning all the way orange. If you fertilized the tree around the same time it was developing fruit, that could have affected development of the fruit and adversely impacted flavor. Fertilizer will divert too much tree growth away from fruit development.