Nest Learning Thermostat 2 wires heating sporadically

[BC652]

I just installed 5 3rd generation Nest Learning thermostats.  I have in-floor radiant heating.  (Red and White wires only).  Easy installation, but the heat is not working properly.  One zone, which still has an older thermostat, is not working at all.  The zones with the Nest are heating sporadically, and very, very slowly. Some of the zones with the older thermostats work fine, others are having the same issues as the Nest zones, or not working at all, as noted above.

In the equipment section of the app the wiring is shown as "heat" for the W1 (white wire), and "power" for the RH (red wire).  I have no C wire

The thermostats are receiving power, are connected to Wifi, and power up the boiler when the heat is turned up.  But, I am not consistently receiving heat, and zones that might have taken 30-60 minutes to get up to temperature are now taking 2-4 hours.

Can anyone provide answers on why the system is not working properly?  I did not have this problem prior to installing the Nests.

[CoolingWizard]

@BC652 , you need to verify the power of the control system being sent to each Nest Thermostat location. Also, how is the system set up? Is there a single boiler, and multiple zone valves that open and close to flow hot water into a floor zone? So, are those water valves powered open and self closing? 

Or, are all the thermostats connected to a main controller located at the boiler and the controller open and closes the water valves?

AC Cooling Wizard