Performance issue with aggregator

I have many external feeds (over 50) loaded into my 4.7 site through the aggregator module and am having significant performance issues when I try to access the module and make any changes or add in new feeds. Most commonly I get a "Error: host not accessible" page . Am also getting server error messages. With so many feeds I am also experiencing problems with the cron update. Typically only about half of the feeds are updating in any one update . Am not sure if I have aggregator2 module. I am using the core module which comes with 4.7