Hard starting 1985 300D Help! Glow plug / Injectors ....

[Hip001]

I've had this car 3 months now with very lil problems and 215k on the dial. Now it is hard to start. Turn the key on and off multi times and the glow plug dash light sometimes lights and sometimes not. And when lit it only stays lit for a couple sec.
I went by "diesel Giants" How to check/change Glow plugs. Only one of the 5 was under 1ohm. So I have a set ordered for pick up today.

My next question is injectors?
I am not sure of the complete service history of the car but it does seem to idle a lil rough. I watched a video clip on the same site and he said it should idle smooth like the example car did after installing "Bosio" injectors. Do you guys use these or the German OEM Bosch? How often should they be changed? I'm pulling them out tomorrow to go have them pop tested at the local shop. Also will running Bio B99 or Veggie blend affect/cause these issues?

Thanks again!
Hip