I have had glow plugs leak around the seal or become loose causing a huge fuel leak as well as causing engine operation to degrade.
You might want to start the engine and observe around the plug to see if it is leaking....run at full throttle.
Or just change it and see what happens.

Also....I have had a lot of trouble with Du-Bro fuel line now that Prather is out of business and their fuel line is not available anymore.
The DB line is very soft and has silicone chips in it as well as powder or chalk to prevent it from sticking together.
Flush all lines before using them.
Also....when installing the DB fuel line....the nipple on the engine can gouge out a 'flap' on the inside of the line which flutters over the opening of the nipple causing weird operation.