I'm curious about why you are so worried about your own SG level being at 1.027? Mine varies some as I sell coral and use water from my tank to fill bags and containers and the auto top off adds fresh water so my salinity goes down. So my SG runs from 1.025 to 1.027 and on occasion even a bit higher. My tank has a huge variety of corals and other animals in it. Some animals that other reefers might not even consider keeping. And they all are doing quite well. In fact my rock flower anemones are even breeding! I've had 2 rounds of babies and I've gone from having 5 RFA's to 17 with the first spawn and over 35 with the second spawn. So 1.027 isn't an issue to worry about.
You need to calm down and do some comparison work with others. Heck, I almost never even use my refractometer any more. I calibrated mine using calibration fluid (using RO water and setting at zero is a VERY poor alternative IMHO). Then I took my tank water and it read 1.025. So I tried the same water with my cheap swing arm hydrometer and as you can guess, it was wrong. It read 1.029. So it reads 0.004 too high. I labeled the hydrometer as '0.004 high' and now just subtract the 0.004 from whatever reading I get. Every 3 months after that I calibrated the refractometer and occasionally it needed a small adjustment. But every time I calibrated it, I would also do the comparison test to the hydrometer. And guess what? Every time, every 3 months for 2 years the hydrometer read 0.004 too high. So I started doing the test every 6 months for a couple of years. And now I do it every January just to be sure. It's been almost 8 years now and the hydrometer still reads 0.004 too high. So my refractometer sits in a box with my PAR meter, a couple of thermometers, a pH meter and a spare hydrometer (this one is labeled 0.010 low) and the refractometer only comes out once a year! I test my water every week just to make sure I'm in the safe range.
