[Cougra]

As far as I've seen that's a common problem with the test kits available to us. I personally use Hagen test kits and they have corrective colour charts for freshwater or saltwater depending on which the test is done with, is there a similar correction chart with you test kits?

I also haven't had good results from test strips in the past. I found that they were way off.

Another possible explaination would be the expirery date in the liqud regent test kit. The strips have a longer shelf life but the regents I find a slightly more accurate.

Salifert has the best reputation when it comes to test kits if that's available to you, you may wish to pick one up or try to get the LFS to test your water for you to see if they match either of your results.