Good run down from PatriceJ on the possibilities ... thanks PJ, you saved me a lot of typing, and made a lot more sense than I would have!
A further suggestion ... when making all the adjustments as she has mentioned ... make only one change at a time. Otherwise you will not know what made the difference!
And very much so ... write down the final winning combo, then next time, you can start there for your initial checks on the test strips.
Remember, the different fabric/batting/thread combos from one time to another can alter your settings/results. Likewise, when doing your tests, make sure you are replicating the quilt itself for those fabric/batting/threads.