Hello and welcome to BYC!

Glad you joined.
VetRX is nothing more than glorified Vicks VapoRub and will do nothing to cure a respiratory infection. It
may offer some breathing relief. Tylann50 however, will cure most respiratory infections. It should be administered orally after drawing it out of the bottle with a small gauge needle (22-28) and syringe.
For sour crop I like acidified copper sulfate in the water. But it's best to work towards prevention versus a cure. I feed fermented chicken feed every single day to my birds. It has healthy probiotics in it that help keep the gut balanced.
Having a good broad spectrum antibiotic on hand is also useful. I use amoxicillin in the form of fishmox that you can get at fish supply stores.
Roundworms are also the most common internal parasite in chickens and are easily treated using liquid Safeguard goat wormer or piperazine citrate.
A good general use antibacterial spray is Vetericyn Plus. You can also keep a bottle of blukote on hand.
I'd also invest in a pair of heavy duty plier style dog nail cutters. They work great for trimming nails and spurs.