Please help my Shubunkin
Please help. I have been told to and have used "General Cure", contains 250 mg Metronidazole and 75 mg Praziquantel per packet. I used 3 for my 30g tank (per instructions) treatment last night for Shubunkin (5") with very red patch at base of gill. First noticed very slight light brown color at base of dorsal fin, fin clamping and the fish gasping(few days ago). Then I noticed the redness on gills and now at base of bottom fins, I also notice a small white node or something the size of large salt grain on the redness in both locations. The red on the bottom looks round and protrudes from the fish. The fish tries to eat but I can tell he/she is very uncomfortable, the mouth motion is also not normal, seems like mouth gets stuck closed sometimes. The fish does dart around at times and mostly sits still near bottom of the tank.
I have recently (2 weeks ago) added a new smaller (2") shubunkin. Prior to adding the new fish the water did need to be changed, I hadn't done it for a few weeks. I noticed the pH was low but the old fish (we originally found him in our outdoor pond) always did fine but thought new fish may not do well because it came from 7.0pH evironment, so I added something (I forget the name) to raise pH.
So I did the water change and added the new fish (after floating him to get acclimated and adding some existing tank water), made a mistake and added the water that came with the new fish to the aquarium. The new fish came from an outdoor pond/fish store. I also put in a small piece of plant material for them to graze on. It is one of those oxygenating plants for outdoor pond (which I do have, but no fish because it's only 18" deep - which is why we had to take out the now sick Shubunkin, he wouldn't have survived the winter). Promptly removed plant after they showed no interest (a day or two). The new fish (much smaller) chased around the older fish for a couple of days and then they got used to one another, chasing stopped. I do believe the older fish was slightly stressed by this, even though he/she is much larger.
Person at pet store suggested it is probably a parasite and suggested the above medication. I also added some aquarium salt 4 tablespoons predissoved and added it slowly over 12 hour period.
I have also attached two photos. The fish is beginning to look like he/she is losing weight and getting "flat" color. The other fish looks healthy. Also it seems to me the fishes skin looks thinner, especially around or on the head/gill area.
Aquarium - 30 gallons
Filter - Whisper Power filter 30
Black plastic mesh media in filter
Has been established for 7 months
Using dropper type
Ammonia - 0
Using Laguna brand test strips
Nitrite - 0
Nitrate - 40
PH - 5.5-6.0
Alkalinity - 80
Temp - 68
Hardness - Soft water or 25PPM
Any advice would be greatly appreciated, this fish is special to us. Also, I have recenlty read using pH products is not good, any suggestions on how to raise pH?