First o all, do not rely on those sticks are they are unreliable. Drops are more accurate. The sticks could have been giving you wrong readings.

The fins desolve by themselves after the fish have been dead for a while, so I wouldn't consider that a symptom.

Medicated food never hurt, however, the most effective med food available is the one you prepared yourself. That is taking a little bit of tank water in a cup w. med and mixing it up w. food. That works from the inside out as opposed the regular medications that are proven to be of little effect since most meds cannnot be absorb through the skin of the fish.

I would check for sluggishness, hemorrhagic septemia...

How often do you do water changes (WC)?

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GUPPY STRAINS I'M BREEDING:

Blue Grass
Blue Grass Swallow
Metal Blue Grass Swallow
Red Grass
Red Grass Swallow
Neon Blue Giessen/Ribbon
Japan Blue Blue Grass
Japan Blue Wild
Neon Blue

Strains I developed in my fish room:

HB Yellow (own line)
Platinum Pink Blue
HB Blue Leopard
HB Leopard Multi
HB Red Crowntail