Pic's speak a thousand words...

It's hard to say if this is where you should be taking the temp's or not.. as i can't really tell how large they are.

If those readings are 6" below the light...how far are your plants from the light?

what stage is she in?

reducing your light cycle to 16/8 is not a bad thing it just means the plant will go into its flowering stage sooner and slower...as opposed to staying on 18/6 and cutting straight to 12/12.

Need pics