blood on longfin bn fins??

hi guys,
i am the proud new owner of some gorgeous longfin marble bristlenose They are my pride and joy

I have just noticed today (friday, purchased wed pm) that most of them have some red 'blood stain' looks on their fins. Only the pectoral fins seem affected.
There is no actual bleeding, just redness.
Looking at photos from day one, still in their bag, they didnt seem to have this???

I have heard the reddening may come from ammonia, but i have tested my tank twice today and its definitely 0.

Could it be my ph? Maybe too much higher than they are used to?
What can i do about this, apart from my usual weekend waterchange (approx 15%)

Temp 24
Ph 7.2
Ammonia 0
KH 5
GH 7
Nitrite 0

I never used to test my water all these years and have bred many fish successfully. So i dont know if this is ok for bn (admits ignorance)... i know they'd prefer 6.8-7 but my other bn (common and lfabn) have always been happy and healthy in this actual tank.

I definitely want these guys happy and healthy, so suggestions please!!!
Thanks!
~Nina~

i think this may be cause of the colour of the fish and you can see the blood threw the fish's skin imo looks in perfect condition and your water is fine

I agree, the pH is slightly high but not high enough to cause issues. nice looking fish too

grr, the photos just dont show it properly.
Definitely not the bn usual colour, or seethru skin.

It reminds me of when my ammonia spiked and my cories got it on their fins and gills. I did a big water change and only lost one cory.
But my levels are 0.

I tend to agree with the two previous comments, if your really worried you could try a precautionary treatment with PimaFix/Melafix.

Well I half dosed Pima and mela and blood disappearing
My lfs suggested shock from breeder tank to aquarium to my tank, all within three hours.

Thanks all!! Keep watching my lfmbn thread for more stunning photos