You might be experiencing a similar problem that I did with my heat bed. Try hard wiring the heat bed straight to your power supply and see if it will reach above 87C. If it gets up to temperature then the problem is not the heat bed itself. Hard wiring it like that is just for testing purposes though and you will not have any way of controlling it.

I think your problem could be from switching to a newer version of Marlin to use auto bed leveling. I found out Makerfarm uses a different thermistortables.h file than the newer versions of Marlin. Copying my old thermistortables.h file from my original Markerfarm configured version of Marlin over to the new version of Marlin with bed auto leveling fixed my problem with the bed not heating up right.