I have several 30ml. bottles I bought in 18 mg. I find them too strong nic. wise for evening vaping. The ones I bought locally I just purchased like amounts of 6mg. juice and added it to the 18mg. to achieve a 12mg. strength. Can I add pg or vg to the others to drop them from 18 to 12? If so what formula would I use ? Does this sound viable or is there a better way? Thanks Dave