re-coloring advice

here's the background - I'd been dying my hair red for 3 years, I recently dyed it back to my natural level 2 dark brown. This was maybe 2 weeks ago? I used a semi/demi. Since then I've noticed I misseed a few spots (no  I dont' mean red undertones, I expected those and like them, but I litterally missed some spots) and I was wondering if it would be too soon to re-do it? My hair is in good condition healthy no damage to speak of, but thinning from a chronic health issue so I don't like to risk the strength of the roots.

Any thoughts would be appreciated.

I agree, just do the spots you missed (I'm assuming they are on your length, not your scalp so much, so thinning from the scalp is not too much of an issue for this).  I'd do them soon while the color will still match.  Since you were red for so long your hair will be porous and if you wait the color may start to wash out and be harder to match if you only do the spots.