I can offer what natural methods I use (successfully) for treating humans with fungal infections, as I have never had a chicken incur a fungal infection yet. Very often (thought not always) the information is quite parallel.
Considering vent gleet is a fungal infection (which is extremely different from either bacterial or viral infections), the use of molasses is alarming to me. Fungal issues like these come about as a result of the balance of beneficial and non-beneficial organisms of the digestive tract falling out of its healthy ratio. I have no idea what you've been feeding them prior to gleet cropping up, but proper diet very important to preventing this from reoccurring in the future, so please tell us.
Fungus' chosen food is sugars. Anything containing simple sugars or which breaks down into them (that is starchy, carbohydrate foods like rice, pasta, any tubers such as potatos, yams, etc) will feed the yeast, which is exactly what ought not be going on right now. Unless there is some very specific and special property of the molasses allowing it to damage the specific species of yeast that I am ignorant of, this is about as bad an idea as trying to treat a yeast infection with antibiotics. Both literally make the yeast problem worse by making a more suitable environment for the yeast to thrive. So by giving molasses to all your birds, including the ones without symptoms of yeast overload, you may be pushing them closer to it.
Whenever treating any other animal suffering yeast infection, be it interior or exterior, removing carbohydrates - period - from the diet in the very short term will aid inputs like the ACV from another angle; the ACV realigns the pH to a place where the yeast does not thrive but other beneficial gut flora do, and the lack of sugars starves it out. Yeast is EXTREMELY persistent and tenacious stuff, so coming at it fast from multiple angles is best to not give it a time to adapt or get a breath, so to speak.
For the internal factor here, do continue dosing them with ACV, and make absolutely certain that your probiotic source (the yogurt):
1) really truly has LIVE & ACTIVE cultures. This is because tons of companies are swindling liars and they just claim to have living probiotic strains when they actually pasteurize and kill every organism in the yogurt without then reinoculating with Lactobacillus and other species. The yogurt is useless to their recovery without those beneficial bacteria.
2) does NOT contain sugar or other sweeteners. Only plain yogurt, or yogurt you've allowed to sit out until the sweet taste has gone away (other bacteria eat it up, thus the taste is gone). Again, if you're feeding them sugary foods you're doing the birds no favors by feeding the yeast.
I don't know about the fermented mash. I take it this is a processed product you bought? I'd avoid this as any "mash" product is just grains (ie carbs) and feed them on a variety of meat scraps + moderate fat scraps + gently cooked egg + all the leafy greens they will eat. This denies the yeast any sugars outright, and is only for the short term. They should have carbs and sugars from fruits and seeds in their diet under normal circumstances, once the gleet is dealt with.
For external treatment of the vent area - if the vent looks at all irritated - clean it thoroughly will water only. Then dab RAW ACV liberally and thoroughly onto the skin of and around the vent. I only recommend Braggs at this point unless you made it yourself. Once the ACV is on, using a clean Q-tip or something similar, dab on some of that same yogurt you feeding them. This helps to recolonize the area with the same beneficial organisms which can then migrate up into the gut.
