I have 4 computers (iPad Pro, MS SurfaceGO, two HP G71-340 laptops, an iPhone 11 and a Galaxy6 phone in my home all using a Spectrum modem and router (replaced two days ago by Spectrum to fix problem, but didn't) Rarely are two of these using the connection at the same time, and very rarely downloading anything. Distance from any one of them to router location is less than 40'. Incoming Spectrum signal at the modem is 110+ Mbps. At one HP its download speed is consistently over 100 Mbps and the other is consistently about 38 Mbps. The iPad Pro is consistently over 100 and the iPhone 11 is always in mid 20's Mbps.(the last three are sitting together on my desk.) What can I do or look for that will speed up the slow ones, and why the wide differences?