Since you started with the worming, I would continue with that. It can't hurt and you can then rule out worms. The only time oil is recommended is if the crop is impacted and the only type of oil to use then is Mineral Oil. Crops are going to feel funky all day long so you cannot judge them at any time during the day. The only rule you can follow with a crop is that it should be completely empty in the morning. If it is, then it is working properly. If it still has something in it, something is wrong.
Impactions will feel like a hard tennis ball in the morning. When the crop is hard but you can actually squeeze the contents like puddy, it is called a Doughy Crop. (this is a type of yeast that grows out from the lining of the crop). A soft squishy crop is another type of yeast infection which remains sloppy and squishy and sort of floats around in there. Many times you will feel what you think is scratch or grains deep in the crop with a sour crop. (these are yeast colonies).
Get in the habit of feeling crops first thing in the morning. Check everbody's crop by running your hand down the front of the chest of each bird. They should all be flat first thing in the morning. Not a morning goes by that I don't check crops, I have had way too many crop issues over my years and it's best to catch them early.
So, all this being said....continue to worm your birds. Order some Copper Sulfate from one of the above retailers or call TSC and see if they carry it? I am not sure if they do or not. If you definitely know how to safely vomit the bird, do it but be extremely careful, not all birds can handle this without aspirating. Use probiotics or even ACV in the water (1 tablespoon Apple Cider Vinegar per gallon of water) and when you get the Copper, get them all on it. (1/4 teaspoon Copper per gallon of water, new batch daily, use for 7 to 10 days max.) Use probiotics for one week after Copper because it scrubs the crop and intestines clean of all digestive enzymes and bacteria.