Advice for a newbie...here is my setup so far

[Snaz]

You should test your water regularly but certainly a new tank and one with dying stock should be tested every day. Ammonia, nitrite, nitrate and pH. The difference between 1.020 and 1.025 is huge and should be looked at first, likely your testing method is wrong... Refractometers usually have a focus ring so you can focus that white/black dividing line to razor sharpness so you can get an accurate measurement. YouTube should have instructions on how to read a refractometer.

Feeding twice a day sounds excessive and could lead to high ammonia, nitrate and nitrites in new tanks. Also feed a variety of foods for good fish health. Mysis, plankton, pellets, brine shrimp should be in rotation.

Also make sure your refractometer is calibrated, I tested mine recently and it was out 0.003 points!