Having issues with my propane flow from my coach propane tank to my Blackstone BBQ and propane fire pit. My quick connect on the coach is placed before the coach regulator. Both the BBQ and Fire pit still have the regulators attached that came with them. On both units the flame will burn for about 15 to 20 minutes and then the flame decreases and finally goes out completely. Any help with what the problem might be will be appreciated.