My angels fins is not normal what should i do ?

Hello
I mentioned this before but I don't get any good answer maybe I didn't ask it well or I my pictures wasn't clear
I have 4 angelfish in 30 gallons tank I think they are 3 or 4 months old and their sizes are between 1 and 0.5 inch from tail to nose I have them for 2 months and 14 days
When I bought them they were doing fine for one month they have some issues with zebra danios such as under belly fin nipping but two of them grow them back except my black lace angel after one month my black lace angel and veil tail( maybe a koi can't tell ) started to grow un normal my black lace angel case was worst so I post it and I get answered that treats him with antibiotics and antI parasites flakes so I did they first get better but after a while their upper fins started to grow bad again and after a while it grows like something that I saw in internet as fin bent 3 of my 4 angels have this problem 4th one (my marbel angel is okay) but the other 3 have some deformity on their upper fin

This my veil tail( maybe a koi his head is getting yellow) as you can see his upper fin is little bent and looks like he has fin rot but there is no signs of fungus, bacteria and parasite its just grow like this one of his under belly fin was nipped by zebras but it grows back with ugly shape

This is my blushing ( I think ) angel his fin grows and now start bent his under belly was nipped to but grow back very normal

And this is my black lace angel he has the worst fin case his nipped fins never grows back and his upper fin is deformed very bad and I think its make him troubles with swimming his always facing the surface with 90 degree angle
All of them are active and feeding well for now
I giving them normal flakes, a product calling red mico and discus tropical food there is 3 times feeding in day and one day fast in week water parameters are normal 0 ammonia 0 nitrite and 10ppm nitrate there is 2 30-40% water change with vac in week my ph is 6.8 I keep my temp between 26-28c and my water is hard( do you think its hard water causing this?? my kh is 80 and my gh is 75-150 sometimes reporting 200!!) I use blue wave05 filter and I have plants
Sorry if this is too long I just give every thing I just want to know what should I do with them so their fins get better or not getting worse if there isn't I want to know this is genetic or something else I didn't buy them from some where very clean and feeling happy and sad about it

 

Did you treat the whole tank with the medication? How long did you treat with it?

 

For 10 days my lfs told me to give antibiotics flakes for 6 days and give immune booster for 4 days I don't put my black lace (he has this problem that time) in qt because he always like to stay near my filter in the other side of the tank far from others so not my angels or others never got the flakes and very small parts of the food that he couldn't get it ended up in my filter

 

So all the fish ate the flakes? Did they say anything about feeding the medicine again after a week? What was the "immune booster" they gave you?

 

No not all of the fishes ate the flakes( except immune booster) and they say nothing about after 10 days ends(my fish starts growing fins so I didn't ask) they gave me flakes in two small envelope from two open packs and they told the immune booster is make fish to heal faster and not feel stressed after medication and its good for other fishes too but they told me not to give it after 4 days over

 

What could have happened is whatever disease was causing trouble with your angels remained in your other fish and then when the Angels stopped the meds the disease was able to reinfect them.

 

So I should buy medicines again and treat all 3 of them this time?
How long should I do this to make sure the disease is gone?

 

I would use the same thing that worked before, just get enough for all the fish.

 

Okay I'm going to buy some medicine for them if anything happens I report it here
Thanks for advice

 

If the other fish won't eat the flakes then you may need to get a form of the medicine that treats the water, since you need to get the medicine into them somehow