Well, you know the standard..35 is the right size for two fancy golds ....alone. Pushing it for 3; and not sufficient for comets, commons and koi.
They are super messy, and they are heavy users of the oxygen and electrolytes..
and warmer water to split the difference with tropicals will cause them to produce more waste because digestive problems. One of the 4 big reasons that you don't mix golds with tropicals.
And then you add the poor sharks (which are a large fish to , nei?) are on the bottom where it all comes to rest...yuk!
The golds may be in a growth spurt and destroying your parameters....
Start changing water with a 50 now and a 30 every other day til you can test and see (better safe than sorry). I am always adding an extra change when I am out of a kit.