Bed Heater Upgrades

I have been printing for some time with a Creality Ender 5 using the stock, magnetic bed. I recently have had "adhesion problems" with no changes to the settings, plastics etc. The bed has been cleaned with acetone. I installed my glass bed with adhesive glue and the problem got worse.When I checked the bed temperature against a thermocouple the center was off by around 15C. I increased the temperature by as much and have been printing again on the magnetic bed. But what remains disturbing is the variation in temperature at about 5cm from the center--about 10deg. The bed heater on this type of printer is all concentrated in a small area at the center of the build plate. I was wondering if anyone has experience with1) Measuring bed temperature about the build plate on the creality printers2) Upgrades for more even heating. (e.g. Keenovo)It seems like this would be one of the more critical parameters for printing.ThanksFritz