Spikes turn brown and shrivel

[khill]

I have had some successes and quite a few failures recently with my orchids. I have several plants of different genera that the spikes start great and then turn brown and shrivel.

What generally would cause this? Water quality? Not enough fertilizer? Temperature change? Pests? I'm at a loss. Now, I do grow outside in SW Florida so this time of year the humidity/temperature varies a bit.

Several of my dendrobiums (phal type) had a successful spike and then a failed spike. My Catt. Yellow Bird had only 1 successful spike (flower ended up looking kinda funny) and about 6-7 dried up and shrivelled. I currently have a phal spike that looks like its headed in the same dried up direction. Also one of my Vandas--same thing.

I am sure it is something I am doing, but not sure what. I don't fertilize constantly--maybe about 1-2 times a month with general orchid fertilizer. I try to water with RO or rainwater. Sometimes I have used our treated well water (salt), but only on a few occasions. I am starting to feel like a failure at this, but I have had some beautiful successes. It's the only thing that gives me hope. Any ideas?