New forum member looking for advice and input

hi everyone, i've been reading posts and suggestions on the forum for some time for various issues *** had with my tank over the past year. figured i should probably sign up and ask some myself.

Here's my tank setup. 55 gallon bow front with 2 marineland emporer 280 filters running.
I'll run down some of the stock but unfortunately when i first started i chose at random being completely new to aquarium keeping. So i may not know the exact species of the first couple.
all these guys are adolescent in size i would say. about 2 inches in length on average.

2 - yellow labs male and female i do believe. The female has some black but far less then the male
2 - jewel cichlids
2 - electric blue. one larger male and a smaller female. bought both at the same time but the male has really outgrown his counterpart
2 - blood parrots. Bought these as babies and they are just now starting to show some color.
1 - Aulonocara stuartgranti
2 - females purchased with the male stuartgranti
1 - male peacock similar to the stuartgranti but i dont know the species. redish purple in color but has never shown the full potential that was boasted about by the LFS
1 - Clown loach
1 - chinese algea eater

I know that seems like alot of fish, and i'm at fault for th impulse... oooooo he's pretty must have em buys. They all seem to be doing well.. everyone eats, and for the most part everyone plays nice. The electric blue male and a parrot fish hate each other and fight a fair bit but they dont seem to be doing any damage to each other. scolding them doesnt work. :x

my concern is the female tellow lab. she's always been hiding vertically in what ever she can take refuge in. the male torments her on site. she eats with the group fine, and he leaves her alone then, but most times i'll find her at the top of the tank facing up with her snout towrads the top. I was concerned that she was "fluking" is it? gasping for air? but she comes down and swims and eats normally. is there any recommendations anyone can give to a newbie with this setup. i'm learning as i go.

ammonia and nitrite are - 0
nitrate tonight was about 20ppm but it's due tomorrow fot a water change. i do one smaller one, about 25% mid week, and a larger one o the weekend when i vacuum the gravel and rearrange the decor to try and stop any territorial aggression... on the advice of my LFS

I should also add that I had two strange fish deaths this month. I purchased two smaller clown loaches ( about 1") to keep my larger one (2"+) company. about a week later one became lethargic and hid. wasnt feeding and became weak. he would swim awkwardly and was unable to fight any sorty of current. he passed in the hospital. The second loach of the same size was still behaving normally. about 2 weeks later he began to show the exact same signs and it passed very quickly.
The larger loach is fine weeks later.

sorry for the long long post. if you made it this far thank you for reading on.I hope to hear from the group and look forward to being an active member and learning from everyone.