What does 0 memory grants pending, but low PLE, high lazy writes/sec and free list stalls/sec indicate?

My server memory is 100GB, of which 90GB is allocated to SQL server via the max memory setting. I am monitoring a sql server that has got 0 memory grants pending. This means no process is waiting for memory. If this was greater than 0 then it will indicate memory pressure which would get resolved upon increasing the max sql server memory setting. However I am seeing low PLE (page life expectancy), high lazy writes/sec and free list stalls/sec. Does this indicate memory pressure?