This is called a fallback rise and most commonly occurs on 2dpo. It is totally normal and quite common. I get a FR on 2dpo at least half of my cycles. The dip can vary in size a fair bit, that is normal too.
Fresh pineapple always irritates my tongue like that to some extent, regardless of ripeness or part of the fruit. Maybe put it in a smoothie and drink through a straw? That may reduce the effect.