Manny diseases can show up atypical symptoms, symptoms not normally shown. IME – it is very common in diseases caused of external parasites that fish show up atypical indications. Probably it depends on strain of parasite, host response and other factors. The only way to know exactly in this case is to take a sample of the skin and analyse under the microscope. Even then, it can be difficult to distinguish between primary and secondary pathogens. IMO – it is important to look at the whole picture, behaviour of the disease, fish behaviour, used methods and so on – not only looking on a picture. This can be (I´m not saying it is!) a primary infection of ich followed of host response and/or a secondary infection of some other microorganism forming this for ich atypical visual indications. Every fish is different, every parasite is different, every water is different, every microbial sub population is different – with other words – everything is different.
If it has been my fishes – I would do an antiseptic bath (I think that rally is that- correct me if I´m wrong) followed of a TTM. TTM can be done in a easy way with help of two 10 – 20 litres bucket and two small powerheads. Prepare both buckets with 50% new water and 50 % from the DT. Let the powerhead circulate. Put the fishes in bucket 1. Cover – it should be dark. Next day (day2) transfer only the fishes to bucket 2 - clean bucket 1 and powerhead 1 – fill up with 50/50 water again. Day 3 – net the fishes and put them in the bucket 1 again, clean and prepare bucket 2 and so on for 7 – 10 days. Do not feed, keep them dark. If needed – bath antiseptic between the transfers.
Use the information you get in this thread and decide the pathway you will take – but do not forget to comeback and tell how you did and how it ended. We can all learn of other experiences
Sincerely Lasse