Phalaenopsis Growth Stalling and Bud Drop

[naturally_stylish]

Hi,

This is my first post so please be gentle!

I have been collecting phalaenopsis and oncidium orchids for a little while and have found this site invaluable for its depth of information. Normally I have been able to read about a solution to any problem I've experienced but I would love some expert one on one advice to this problem.

Over the past month all of my phalaenopsis orchids which had started flower spikes have stopped, some of the spikes had buds but these have all shriveled up and died (bud blast). Others have small spikes between 1cm and 10cm but they are stuck at this size.

This is my first season growing orchids from seedlings as in the past I had bought flowering size so I'm not sure what I'm doing wrong that is causing the problem. I only had one oncidium in spike but that has flowered with no problems.

The plants are all grown inside my home and I live in QLD Australia with day temps of around 21 celcius and nights around 19 celcius. I have no gas cookers or fires and the plants are not being moved around or receiving any cold breezes. I use a combination of perlite and bark as my growing medium and I fertilize fortnightly using 22-8-12 one fortnight and 12-12-20 the second fortnight.

All my plants are healthy with good root systems.

The only thing I could think of was I had the outside of my home sprayed for pests around 6 weeks ago, could this of caused the problem and would it still be an issue?

I grow the orchids as I love having their blooms around my home so I hope someone can help as its very frustrating!