On your phone or tablet get an app to test the wifi strength in the area where you store them overnight eg bedside table. I use Wifi Analyzer by Kevin Yuan. The free version is good just gets ads on it but not intrusive.. Check signal strength and what other Wifi signals are sharing or very close to your wifi channel..
I am assuming that they changed the modem you use and that may not have the same strength of signal output as your old one particularly if it only has internal antennas. If the signal is poor try adjusting the position/orientation of the modem and retesting the signal. Try first by facing the modem slightly away from it's previous alignment then going to the overnight area and seeing what the signal is like. Keep doing this until you have completed about a 180 degree arc from it's original position. If one point is strongest then after the testing is complete leave it there.
Also if the height of where the modem is placed has changed try placing it back at the old height and again you may need to redo the alignment tests at varying heights. The modem should be roughly at the height of where your phone will be, roughly means within 60 cm up or down...up is generally better as the closer you get to the floor the more clutter the signal needs to go through.
If your modem has external antennas you should try adjusting them as well to test the signal.
If your wifi channel is sharing it's bandwidth with a lot of others you may need to try adjusting the channel it is on. To do this you will need to enter the modem's setting and in the wifi section go to the channel and setting it to one of the channels that was free of others or had the least amount of others. For the 2.4 Ghz channels the best three to try for are 1, 6 and 11. For a bit of a read about it see here https://www.extremetech.com/computing/179344-how-to-boost-your-wifi-speed-by-choosing-the-right-channel. Originally it is probably on Auto. You should also set the signal strength to 100% while there if it isn't already.
This should improve the behaviour of your phone and tablet power consumption and wifi speed particularly as they won't have to expend as much energy trying to get the best signal. If you set the channel on your modem in many of the later phones and tablets you can lock them to that channel and also turn the searching for other networks off. If you can't do this don't worry though.
Oh and make sure your GPS/Location is turned off in your phone and tablet as this will certainly drain the batteries fast.