Five of my Phals had recently begun to spike. Two have continued and are growing fast and furious. Three spikes started to poke out and then abruptly stopped growing though they are still green. The plants themselves look fine in each case, with both new root and leaf growth.

Is this common? Are there specific issues that might cause aborted spikes that I can address in my care?

I am windowsill grower and all of these particular Phals are in the same location - same light, water, fertilizer, humidity, etc.

Thanks for any advice!