Moving this from Parenting...I know they need to be firm but our current one is like a slab. Dd gets a very livid red mark on her face which lasts for a good hour or so when waking. She's not a great sleeper, and I'm wondering if uncomfortable. Our current one is from the John lewis Every day range. Is it worth buying a sprung mattress...or do they all conform to the same firmness?TIA