Looking for suggestions

[Strap]

I have read several articles, and still not sure what I need to do, and how. – Where I live the relative humidity is very low, often in the single digit. My concern is replacing fluid, as it is used up from plant activity and evaporation. If I keep replacing it with the mixed solution, and the water evaporation has been the main loss, won’t the solution keep getting stronger and stronger? – If the loss has been to plant activity, and I add plain water, won’t the solution keep getting weaker and weaker? – I know there are some elaborate ways and equipment for monitoring, but what is a good, inexpensive way? What works for you ?