Phal Culture in Houston

[Gardening in WM]

I agree with Estacion.

But it could be a variety of different reasons.

Dendrobiums and Cattleya's grow well with you you say - these can tolerate colder temperatures than Phals so it might be as simple as you are keeping your phals too cold in winter. You might have even read this is beneficial for phals but phals are tropical plants that require warm temperatures all year. They are light sensitive orchids.
You might have read that reducing temperatures below 65 F degrees will cause them to spike and although that is true, it only happens because you are causing the plant stress. It is not something I personally would recommend anyone does on purpose. Orchid nurseries will do this to get their plants to flower so they can be sold better but it stresses the orchids and they might sulk for several months afterwards as a result. It is best to grow them warm and let the seasonal light changes dictate when it is best for a phal to flower. A healthy phal will flower much better year after year if grown warm all year long (under 80 F) opposed to one that you force to flower by lowering temperatures below what they would experience in nature in a tropical climate. If it is done at exactly the right time of year it can be beneficial but otherwise it will just cause stress and confusion for the plant.

so it could be the low temperatures causing stress.

I believe the dolomite lime could be another potential problem. Dolomite lime raises the PH of the media a lot. Phals like acidic conditions. This can lock out nutrients. Dolomite lime can also contain lead and although other houseplants can tolerate trace amounts of lead, orchids are very sensitive to heavy metals and it will stress them far more than other plants. Many growers have experienced problems using dolomite lime not just with orchids.

A better solution is to use calcitic lime and epsom salt.

Or a cal-mag fertilizer is the best option as it is safe, chelated and contains beneficial iron added too.

You used to use tap water and horse manure and had excellent results.

Then you switched to rain water and started adding the dolomite lime to compensate for rain water not containing enough calcium and magnesium which is when your problems started.

Maybe just stick to tap water which contains enough calcium and add 1/8 tsp of epsom salt/gal to add the missing magnesium

If you cannot find horse manure and you liked the results you can substitute horse manure for chicken manure which is much easier to find.

But in your climate you should be growing them indoors where I would not recommend using chicken manure as it smells.

So my nr 1 tip would be to ditch the lime and substitute it for epsom salt + tap water or epsom salt + calcitic lime + rain water. Then again if the lime is not causing any problems fro the dendrobiums or cattleya's it would indicate it could just be the wrong temperatures and possibly like estacion has mentioned too much light for them as a zone 7 will be much brighter than a zone 9.