Parasites?

[Ursi]

I've got a rather big problem on my hands, and I'm not quite sure how to sort it.. First off my tank is 260l/69g, my stocking is:

6 neon tetras
5 black tetras
2 ember tetras
2 platys
4 balloon mollies
6 mollies
1 angel fish
2 zebra loaches
1 zodiac loach
5 corys
2 bristle nose plecos

My water parameters are ammonia-0 nitrite-0 nitrate-5 (live plants) my parameters don't change. I have a interpet HOB filter that's 800litres an hour, and a canister filter which is also 800L an hour (at least that's what they say the maximum flow is, hoping that's right)
I have an out break of ich, and also I have a problem that a fair few of the fish have red gills, I think they could possibly have gill flukes, but I'm not sure, it's hard to see and it wouldn't show up on a photo, but a few fish have it, but only the mollies/ platys.
I'm treating the ich with heat, due to the loaches and all the fish are acting ok, but a few seem lethargic, something just isn't right.
Does anyone know what I can do? Their poop has been kind of stringy, so fat thin fat thin and I think it's possibly either internal parasites or gill flukes? Any help would be greatly appreciated

EDIT: ph is 7.5 and stable, the fish are all eating, and swimming fine

 

[Hholly]

I think the ich attacks the gills. That may explain the red gills. Did you increase aeration in the tank?

 

[Ursi]

I think the ich attacks the gills. That may explain the red gills. Did you increase aeration in the tank?

I already have 2 air stones, the long ones, plus quite a bit of surface movement, shall I increase it even more?

 

[Hholly]

That sounds sufficient. Did you add any salt? They're probably just fighting off the ich.

 

[Ursi]

That sounds sufficient. Did you add any salt? They're probably just fighting off the ich.

No didn't add any salt because of the cories, and zebra loaches, I hope it's just them fighting off the ich and there's not a more serious underlying problem. I did a 50% wc 2 days ago too, tested my water today I'm positive it's not the water causing it. Banged my ammonia testing bottle really hard before testing too. Just hope they all pull through
Thanks for your help