Those radios can consume a good amount of current, so I don't think the 3.3v rail on the Electron can supply the full power transmission rate on the LORA radio.
Try powering the radio from the Arduino power source while connecting the grounds between all units. This should tell you if it's a power supply issue to the Lora Radio.
Also, are you using the same code that you are using on the Arduino on the Electron? I know I had to change some settings to get max range on my RFM95w radios + Photon setup.