It is possible that the tunics were normal. That apart, it would depend on what caused it if it was some kind of infection - bacterial is common, fungal perhaps less so.
Household bleach is basically chlorine (as sodium hypochlorite) stabilised with caustic soda. Unless you use sterilised compost, it's effects will be very limited and will be dependant on dilution rate and soak time, but would it penetrate far except on very prolonged soaking?
I have been trying to germinate some SA seeds and failed, perhaps not least due to a very high fungal spore load (trying to germinate them on paper in petri dishes, this is very obvious) so I bought 100 seeds to try various things.
Soaking the seeds in undiluted household bleach for 45-60 minutes achieved nothing obvious.
Soaking for 4 hours in working strength Fungus Clear Ultra (triticonazole) massively reduced the spore burden with no growth obvious after 2 weeks and counting.
Rootgrow is just micorhyzal fungi, so would have no effect on the actual rot. Niether would it likely be able to affect the normal seasonal root growth pattern of the bulbs.
The only apparent, actual, science that I can find about neem oil is that it intereferes with invertebrate hormones and eating response, so acting as something of a repellant. (Lots of other claims are made, but I can find only claims.)
The only live bulbs that I have come across with slimey outer layers have been a good size, so I have just removed the slime, washed thoroughly and planted, and they have been OK, but it is very few bulbs.
