If your meter is still accurate the answer is the cold resistance appears to be at least twice as much as when new. You could check a new plug with your meter to verify it is not your meter. If you were working from one ground you might have picked up a little more resistance in the measuring loop for example. Next time. I would read one plug perhaps even with both leads on the plug. What you really need here is a measure of how much total current is being drawn through the circuit compared to a new set of plugs. Most of us do not own a meter that will handel that much current. This is somewhat academic but it could mean your plugs are only drawing about 1/2 current. A plug at 1 ohm at 12 volts is drawing 12 amps and getting pretty hot. A plug at 2 ohms at 12 volts is drawing about 6 amps. There is a feature on your meter to measure up to 10 amps or at least on most of them. If you inserted it in the line to one glow plug only it would probably verify your meter was still on calibration by indicating an initial draw of about 6 amps dropping off as the plug heats. If so the plugs are weak. Usually when heat is applied the resistance of a given element increases. Possibly the best quick test is to remove one and put it across the batttery to see how hot it is getting. Watch you do not burn yourself. If what you have posted is right the plugs would be very sub standard in heating . What brand are they? Something used should in most cases be directly compared to a new example if there is any question. Although you knew a cold new plugs typical resistance. One years functional lifespan is quite short for a set of plugs. But thats what you may find to be true with a little more testing unfortunatly. This might be a good post for you to post a little more as we do not usually get a lot of threads about the aging syptoms from this perspective on a set of plugs. Yes this problem if you verify your readings could easily give you the ratty starts but you already suspect that. Plus the subject is timely for a lot of people as the cooler weather is on it's way for some of us. It is really important as craig states to have the engine cooled to ambient temperatures for the resistance measurements to be accurate as well.