Use the bloom booster once a quarter, 4 times a year instead of the regular fertilizer. Do not mix.

If you water first the plant will not be able to take in as much fertilizer. Better yet, spray on your fertilizer without pre watering then after a few minutes do it again.

Wouldn't spraying burn dry roots?

If the plant is properly watered day to day, and the fertilizer is mixed properly it will not burn anything! Orchids are air plants. You might be thinking of tomato plants or African Violets. Orchid roots are different...

I suppose like everything else a fertiliser program is influenced by where you are and zone6 might have different "rules" to here.

It is the old when in Rome thing. What might be appropriate here might not be appropriate in zone 6 USA.

Then there is the bloom booster thingo. What do you do in a mixed up collection when there are orchids in various states of growth? I cannot be bothered watering this one with bloom booster and that one with non bloom booster.

Anyway, your question is simplified if you only have three Phals. At this time of year in the Northern Hemisphere in zone 6 maybe you should be using the low Nitrogen formula.

I often mix kelp or earth juice kinds with Grow more 20-20-20. But bloom buster I never mix.

Don't mix fertilizer. What are you trying to accomplish? Are your Phals spiking?

If you are in zone 6, your Phals should be spiking and budding at this point. Additional fertilizer will accomplish nothing.

If you provide more info on what you are growing and the conditions you are growing your plants, it would help.

Jane