Dandelions are deceivingly difficult subjects. Keep shooting.
I don't know if it is just me, but the focus doesn't seem to be sharply on the head of the dandelion as much as the stalk. Might just be my eyes though, I have been looking at this computer screen for way too long!
Focus looks right on to me, looking at the full size picture, ... about as sharp as I'd expect from an 18-135 zoom. At reduced size it looks fuzzy because the subject is fuzz. Also the white of the fuzz is blown out so doesn't show much texture. Exposure bias of -2/3 might not have been enough. Actually I'd guess editing over brightened it ,,, contrast looks boosted.
Suggestion ... If you want to show the hair on small things consider a dedicated macro lens, not a zoom, even one that says it does macro too. Closer would have been better, but at less than 1 meter I guess you might have been about as close as the lens would focus. ... Swiss army knives are great for some things, but not not the best carving tools.
Also, forget that rule of thirds thing. It's a crutch people who want to walk freely shouldn't get tangled up with.
Cute picture....Color is just right.
Thanks a lot to all for your feed backs. Cheers...