Updated the game to 0.11.2 and changed "Low Resolution" to instead be a Quality dropdown menu with the options Full, Half and Third.
Half is the previous Low Resolution mode.
Third makes the textures much smaller, so it might fix your issue (though the textures will look very pixelated, so if you have an alternative device, it's recommended).
Additionally, some players have reported that WebGL games might run better on chrome rather than safari on ipad/iphone.