I used to wear all-white tzitzis, as is the more "universal" custom.
Some time ago, I was convinced to start wearing a blue thread in them, to fulfill the commandment in the Torah to insert a psil techeiles.
Later, I concluded that we do not have a mesorah for techeiles and therefore the companies which manufacture techeiles nowadays do not have the "real deal" dye from the chilazon.
I switched back to using all-white strings.
Did I act properly? Is one allowed to revert to using all-white strings when he decided to put a blue thread in it as the Torah commands? One possible problem I see is that we never go down in holiness, but rather only up (maalah b'kedushah v'lo matah).
In my case I believed initially the blue dye was the real deal, but later concluded that it was not. This case does not deal with someone who believed, and continues to believe, the blue dye we have today is indeed from the chilazon, but yet wears all-white strings anyway for whatever reason. I believe such a question would have to be asked separately.
Notice: I'd like to avoid confrontation about rather the techeiles we have today (be it from the murex trunculus or the cuttlefish) being the real deal. That is not what this question is about; and trust me - I've read into the whole thing. I'm familiar with the arguments.