Have you tried setting DWHTempIn to a fixed value and testing if that updates correctly? Are you sure you have enabled channels 4 and 5 on your thingspeak channel and that the value is within the range you set?
Does it work if you disable the DHT11 and send only the DS1820 temps?
I've not used the arduino TS client but these may narrow down the problem a bit.
(You may wish to change your API key now that you've posted the old one to the internet...)