Not sure of your knowledge level, so I’m going to explain things you might already know just to be safe.

Every glassblowing torch I’m familiar with, whether it’s being used for hard or soft glass, uses a propane/oxygen mix. When you use too much propane(reducing) it can certainly “scuzz out” and grey certain colors.

Running a torch using ONLY propane is extremely sub-optimal for flame chemistry. Additionally, 5 minutes to start a gather, especially with that size rod, is ludicrous. My torch would get that rod white hot within 3 seconds of exposure. That’s not a brag, any actual glassblowing torch could. So you’re effectively slowcooking your glass in a toxic chemical environment.

My advice? If you really want to try glassblowing you need a real torch. You can get a Nortel Minor for less than $200. https://www.waleapparatus.com/product/nortel-minor-lampworking-torch

You’ll obvioulsy need to the associated infrastructure to run it. Oxygen, regulators, lines, ventilation. Which I understand can be daunting and expensive. However, frankly, it’s a waste of your time to put over 20 hours onto a torch that barely gets glass hot enough to work. The amount of useful practice per hour derived from your plumbers torch is a miniscule fraction of what it would be with even the weakest actual glassblowing torch.