gaps and bows in old baltic pine flooring

I have an old (around 1905) timber house with baltic pine flooring. In the hallway the tongue and groove flooring has significant gaps of up to 4 or 5 mm between the boards, though the tongue is still in the groove, and the boards are bowed up along the centre of the board by a few mm and some have a crack down the centre of the board.

Has dirt and grit worked its way into the grooves and pushed the boards apart to cause the gaps and bows?

If so, is there any way of fixing it apart from pulling up the boards and cleaning the grooves?

Any advice appreciated.