Heat bed temp variances

Hello,

Anyone happen to know what the variation from inside to outside on the heated bed on a 1.0 should be? I currently get around 100-105 in the middle 1/3 area, outer 2/3 of that 90-95, and outer edges 70-80ish, is this ball park? I've definitely seen a change on first layer picking up more lately especially on larger prints.

Thanks