The last three are alive and I think you have what appears to be Cyanobacteria.
Refractometers with calibration fluid are preferred. I am not sure who told you they were not accurate but they are easy to use… most auto adjust for temp and don’t need to do it the same way each time. It’s just added a few drops of water and holding it into the light. There is no special way to angle it or such. The calibration fluid verifies they are working correctly.
Since you have a hydrometer, be sure to rinse it well between uses and make sure no air bubbles are trapped that may effect the swing arm.