Bro I suggest you check your salinity with a reliable apparatus immediately... it must be on the very high side since you've been topping up with pre-mixed salt water. It's not hard to understand the concept that in this situation evaporation only occurs to freshwater (the salt will remain in the tank). So by just adding freshwater (treated tapwater, DI or RO/DI) it will help maintain your salinity at a desired level.
However, if your salinity shows anything exceeding 1.027... do not panic, your LS been accustom to it anyway... you can choose to bring it down slowly (say to 1.025 within a period of 2 weeks)... this will make any new introductions less stressed by the high salinity and to keep your maintenance lower. Water is cheap... but salt is not cheap at all
Do keep us posted on this