2 of my fish....A Red Cap Oranda & a white Common (both with white tailfins) seem to have noticable blood veins in their white tails. The other white tailed fish do not. Also these 2 have what looks like blood-like smudges on the very tips of their tails. Here's the readings that I have now!

Ammonia 0
Nitrite 0.25
NitrAte 9 ppm

Tank size 100 gallons
2 Aquaclear 110s
Weekly water changes.....at least 30-40% but yesterday I changed more like 55%
7 fish...(measurements body only)
4 .......2 1/2 to 3 in
1........4 in
1........4 1/2 in
1........3 in

Additives.... Dechlor

Feeding mainly Mazuri Gel Food (plus some Omega one small pellets) I feed morning & evening

No unusual behavior

Blood streaks sounds like signs of fin rot.I'd keep an eye on your fish and salt your tank as a precaution.

Blood streaks in their fins is a natural thing sometimes in mostly white fish. Of course, they wouldn't show up all of a sudden, but rather be there all the time. So, if those veins showed up just recently, its definetely something to think about.
Some fish are much more sensitive to water quality issues than others, and while one fish seems completely unfaced by the water quality being a bit off, that could put enormous stress on another fish.

How long has your tank been running with the current filters on it - nitrites showing up sounds like halfway into cycling. Or you added some fish recently, which could cause small hiccups in the beneficial bacteria. Or you used some medication recently that destroyed some of the beneficial bacteria.

I might have caused a "bump" last weekend as I did a pretty big water change AND siphoned out some gunk in the filters.

I do not think the veins & "smudges" are new. I have noticed them before. Maybe the white tails are easier to see.....although 2 of the others have white tails and I do not see any veins. Think I should salt just to be on the safe side? if so how much would be good for 100 gals. ?

Thanks!