Prep your main reservoir for the week, if that’s the schedule you’re following.
Also prep a second tank of diluted nutrients. This may need to be pH adjusted lower than your main reservoir so it hits your target pH and EC when added.
https://www.amazon.ca/Kerick-Valve-MA052-Float-Adjustable/dp/B0077RAP1I/ref=asc_df_B0077RAP1I/?tag=googlemobshop-20&linkCode=df0&hvadid=292982455806&hvpos=1o4&hvnetw=g&hvrand=15746779309143944639&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9001252&hvtargid=pla-625513493432&psc=1 valves like this come in many sizes. I would mount the diluted tank higher than the main tank if using mechanical float valve, so it is gravity fed. There are also electo-mechanical switches that can turn on a pump when the level decreases, then you can use a transfer pump in your second tank to fill the main one.