Your salinity seems a tad low. If you could at least bring it up to .023, that would be a normal salinity level. Your other parameters look good. Again, a few more questions.
What are you using to test your water?
Liquid or strip test?
When was your last water change? (i know you said weekly but want to make sure)
How much do you change out?
What type of water are you using? Tap? RO
When was the last time you cleaned your filter and media?
How often are you feeding and how much?
Also, how old is the bulb?