Ip cameras can't detect signal

My router is a year old Cisco/linksys. I have multiple wireless ip cameras that are located throughout the house. All have typically worked fine with the time warner wifi signal of about 25/30 mgs.

Spectrum has now come in purchased Time Warner and cut service and reduced wi fi signal while increasing the monthly price. Now 5 of my 8 cameras don't work or work for a few days and then can't detect signal. Spectrum has cut the "juice" to my wi fi but I have not had an opportunity to run a speed test. I don't game or have gamers in my house and stream occasionally and use a cell phone and a couple laptops at a time generally. Right now the cameras are the only thing using wi fi and the signal is apparently so weak I probably couldn't stream if I wanted to. I'm supposed to have 30 mbs. In my plan. I suspect I don't have the 30 mbs.they "say"they're providing.

What are the minimum requirements for wireless cameras,moderate computer use and streaming small amounts of data on and off during the day?