ok running this query

select *

from sys.dm_exec_query_stats qs cross apply sys.dm_exec_sql_text(sql_handle) st

ORDER BY qs.total_logical_reads DESC

. Am assuming that this DMV data is since the last fail over at 6:17am this morning.

1 proc has been executed 999 times with a total_logical_read = 453124440

Having never looked at these figures before its hard to analyse but, iirc that indicates that this proc is trying to read an awful lot of data for only 1000 executions. I assume that wont help memory issues

Looking in sys.dm_os_memory_clerks the biggest user of Multi_page_kb is MEMORYCLERK_SQLCLR with multi_page_kb = 59240

My only worry is that we don't use CLR code on our servers yet CLR was mentioned in the errorlog.