King tide resistance aura interaction

Opponent played resistance aura first causing my spells to cost one more I played king tide causing them to be set at 5 then played gold panner. drew card with gold panner drew another tsunami that was set at cost of 6 while others stayed at 5. Not sure if this is a bug or intended interaction, but at the very least seems inconsistent. I have a screenshot just not sure how to share it.

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