salt placement

[gregzz4]

If you have room like I do, just add some extra aged SW to the sump. Through evaporation your Sg will rise, giving you a slower elevation rate

As for your Sg dropping
It's possible it's dropped as you have added more FW than you thought, or your skimmer is taking it out and being replaced with FW from your ATO

Maybe put a piece of masking tape on the outside of your return section and mark it with a pen or such
Now you can keep an eye on your level

Calibrate your Refractometer to be sure it's all good. Then, before a WC, test your DT water. This will let you know if you need to replace the same amount of water, or adjust it to compensate for a swing in Sg