If you are losing wired ports as well I would check the modem. You can log into most brands by opening up a browser and going to 192.168.100.1 (it's also usually documented on the modem somewhere).
Generally the downstream power (from the plant) isn't the issue but rather the upstream channels. If most or all are hovering over 50 db (max is generally 56 before channel loses sync) then you have a physical issue somewhere. Making sure the run to the modem isn't behind multiple splits from the incoming feed from the house is a good place to start. A good way to check is to plug the modem into the main feed line and verify the upstream channel power. If there is only a single split and the power difference is significant (more than the loss that is documented on the splitter itself) you have an internal wiring issue somewhere (bad splitter or end)