Given your water and the fertilizers you have been using, sounds to me like
you have been giving your roots an acid bath. Not only will this hurt the
roots, but it will also impair the plants ability to take up the micros and
macros. It is not that you are not providing them to the plant, it is the
plants hindered ability to take them up given the low pH of the mix.

If you do not get any other answers you like, try this. Sorry I do not have
time to explain it all, but I am just plain out of time.

First do a real good flush. Heavy watering with clear water, wait a few
hours and repeat.

The next couple of waterings use clear water. At this point the plants
should be looking a little better.

After a couple of waterings start watering with a weak regular fertilizer
such as 20-10-10, 20-20-20, or 15-16-17. (Flush once a month).

After 6 weeks or so start using a fertilizer that has calcium and manganese
once a month as the last feeding before the flush. MSU, Jack's RO, Jack's
Well Water, and Excel Cal/Mag are all good choices. I think Ray sells one
of these.

Basically the water schedule will be reg fert, reg fert, cal/mag, flush.

As the plants return to health, the fertilizer concentration can be
increased from weak to more normal levels. At that point you might also
want to add a bloom booster once per rotation or at special times of the
year, but be careful as they are pretty acidic and I am not sure they are
necessary or worth the risk.

Hope this helps,
Pat B


Next
"solo_voyager" wrote in message
om...
Where to begin? O.K., I have several Dendrobiums (most from section
Dendrobium) that are showing similar symptoms.

1. The thin leafed types begin yellowing at the tips of the middle to
older leafs. Eventually they start turning tan in color, dying back
from the tips.
2. Those with a thicker leaf consistancy also begin yellowing at the
tips or somewhere along the margin, but are much slower in actually
dying and turning tan in color. Some do not begin dying off. They
simply become chlorotic in spots.

I have treated for both bacterial and fungal infections to no avail. I
am beginning to suspect mico-nutrient deficiency or toxicity.

Up here, we have water quality most of you would die for, very low in
disolved minerals and other such things. Visiting guest speakers for
the local O.S. have often recomended that we feed with every watering
because out water is so clean and free of contaminants.

I use a fertilizer mixture of:
A crystaline 10-52-10 with a label assay of:
N:
9.0% Ammoniacal
1.0% Nitrate
P:
P2O5 52%
K:
K2O 10%
Boron: 0.02%
Copper: 0.07%
Iron: (Chelated) 0.15%
Manganese: (Chelated) 0.05%

The other fertilizer ingredient is a 0-10-10 fish based fertilizer
with a lable assay that includes:
Chlorine: 8.0% (That strikes me as high.)
I chose this material because I assume the marine fish base should
supply any and all micro-nutrients that might be needed.

I fill a tub with 6 gallons of water and add the recommended amount of
each fertilizer for 1 gallon. To my thinking this is the equivelant of
adding a 10-62-20 requirement for 1 gal to 3 gallons of water, a 1/3rd
solution. I fertilize at almost all waterings during spring, summer
and fall, and few if any during winter.

Potential causes as near as I can deduce a
DEFICIENCIES OF:
Magnesium
Cobalt
Copper
Iron
Manganese
Molybdenum
Nitrogen
Zinc

EXCESSES OF:
Calcium
Chlorine(?)
Potassium
Phosphorus
Zinc

Can anyone comment or add any insight to this possible problem?
Thx
S V