Orchigiant,

Rotting of new growths may be caused in several different ways. All cause moisture of one make-up or another to linger in the base of a fragile new growth, allowing for perfect conditions for growth of a fungal infection which then will destroy your new growth.
1) Watering late in the day with no wind and low temps.
2) Allowing pesticides/fertilizers to linger in the new growth more than 4-8 hours
3) The leaves on some tetraploid seedling growths, usually unbloomed, are so tight that it is virtually impossible for water to drain out, no matter the temp, time of watering or wind. I have experimented with a seedling now for 6 years. Just when it stopped rotting the new growths, a squirrel got the most recent one! Now I will try again. Roots are not the problem.

After cutting the rotten part out, I treat with cinnamon. To prevent, tip the plant after watering so that all water drains from the growths. Also be certain that the plant is in a warmer and or sunnier spot in your growing area with plenty of air circulation.

I also would not use the Bayer all in One as I suspect it is too strong for many orchid varieties and most certainly the new growths.

Good Luck,

CL

Oh yes-another thing I thought of when I was reading another forum- keep the pH neutral for cym's
I like 7 if I can get it. Dont put Acid solutions (less than pH 7) on your plants.