It looks like the first plant you showed on your website starting from
the top and to the bottom (as far as the unidentified plants go) is
either anachris or elodia/egeria densia. Both are often mistaken for
the other. Anachris is a mostly cold water plant while elodea/egeria
usually does a lot better in warmer waters. The second plant is either
hornwort or myrphyllium and the hornwort also is mostly colder water (I
have only had incredible success with hornwort when the water was no
warmer than 68 degrees fahrenheit) of a plant while myrphillium is
generally a warmer water plant. Except for some fin and tail rot (or at
the very least other fish are nipping her tail) your guppy looks fine.
She will need medicine while she is in the hospital tank until fully
cured. The progressive salt treatment might work instead of harsh
chemicals though. Read up on the pros and cons of both types of
treatments without doing anything but the sooner she is treated the
better. You might very well get a better diagnoses from other users
here but I am just trying to help as best as I can. I have healed fish
from fungus with the progressive salt treatment before and with dip
medications but fortunately since I grew up after starting out young in
this hobby I have kept such good care of my fish that they almost never
get sick so I don't have extensive experience with fish medicine.
Generally the harsh chemicals only work if you remove the carbon
filtration (if you use it - that's because the carbon filtration will
absorb the chemicals before they have any effect) and may kill plants
or sensitive fish and of course might uncycle (kill the good bacteria)
an aquarium and kill invertebrates like snails. Salt can do that
somewhat too so that's why having a hospital tank is important but is
still usually way less extreme than the chemical method. Good luck and
I like your tank's beauty!