mysql cluster with innodb utilizing high memory
The main memory usage in an SQL node is for InnoDB's buffer pool.  What is the value of innodb_buffer_pool_size?  (Use SHOW VARIABLES LIKE 'innodb_buffer_pool_size';)  How much RAM do you have?  Normally, it should be set to about 70% of RAM.  The memory usage will grow until it hits the setting.  After that it will fluctuate slightly as other allocations come and go.