"104" caps testing as 50-60 nF and their use as decoupling caps
I do short the leads for a moment before checking the value  


Right start 



If it is a breadboard PCB, i would put one or two in parallel and still go with it for a low voltage application 5V, 3,3 V.  

Always buy components from reputed shops/sites.   


The tolerances will be +/- 20% for the general purpose capacitors  
for a decoupling application, the exact 100nF is not a must requirement 
if it is for a RF application or a safety application, you would not have even considered using the capacitors without the datasheet