Newly imported products not searchable in admin panel but are on the store front

HI

I have never had a problem with backend searches before but I imported around 150 new products and only around 20 of those are searchable in the admin panel.

I have created a collection of all the new products that have been tagged and ALL 150 of them show under the tagged products in the collection but for some reason only 20 of them show up in an individual search.

All of the 150 products are searchable in the store front. Any ideas how to remedy this?

Thanks

Terry