increase your nutrient solution for vegging. your lower leaves are nitrogen deprived - and this is normal. your height of 18 inches should be fine. if you had heat issues it would be apparent at the canopy level.
you will only have to worry about the smell during fall, the last few weeks of flowering.. one plant wont be a big deal~ but i doubt your garden will be in full bloom then ~
you can order them dirently from Marc Emery via mail order @
Marc Scott Emery #40252-086 Unit DB
PO Box 13900
FDC SeaTac
Seattle, Washington
98198-1090
USA