Fusarium wilt outbreak advice needed

[KatKate]

Where do I start. This summer I have moved to a bigger house and I decided to indulge in my passion and add more Phals from my long wanted list. I have bought several new Phals from different nurseries and stores (Dutch suppliers mainly) from both sources. Before this summer I had already quite a few orchids (Phals, Dendrobiums, Paphiopedilums) for several years and they were not complaining or diseased so summer was quite good until I suddenly lost one of the orchid purchased 1 month before that from a dry rot. I disposed of the remains. Then a second one that was not so far from it (by quarantine principle) and purchased also around 1.5-2 months before that perished from the same nasty rot. That’s where for the first time in my experience I met with Fusarium (purple tissue around the rot for the orchid not known to display purple pigment). Worse comes next. I have discovered the first signs of the infection (stem mainly with roots looking as brown/blackish buds not coming out, and roots - in one case super purple tip of a newly growing root) in several of my Phals. I really do not understand what I do wrong or if it is a Superbad coincidence and they were already purchased this way.
But: those cases were in different parts of the house, scissors for pruning are always well disinfected with ethanol, no water is shared between the plants. Those cases that were really rotten were carefully disposed of. Those cases that are suspicious or with beginning of the dry rot, I isolated them and treating them as much as I can as I want to save them. We cannot get strong fungicides here where I live and frankly do not want to use the dangerous ones, so I use bacillus subtilis “prophylactic” treatment since the “outbreak” started. Bacillus subtilis was shown to prevent and sometimes treat different rots including fusarium ones. I also sprayed 3% oxygen peroxide where the roots were suspicious. I was hesitant to repot the majority of these cases, as the original substrate seems to be ok (good drainage, not decomposing). I have been doing the treatment for a month now. Unfortunately I do not see the signs of improvement so far. Would anyone have an advice on that, please! I am kinda lost and depressed, do not want to throw out the plants preventively, there are all very beautiful and some of them quite rare. Thank you very much in advance!!!!