I doesn't matter from where your visitor is, Click matters. If your visitors clicks on ad and not just click do sign up on that website or buy something than you'll get more money from that click.
English ads would probably pay better, because there is a larger market. Hebrew ads on your site pay less, because the market is relatively small compared to the english one.
If you want a higher CPC you'll have to develop content that attracts a higher CPC. Advertisers will only pay high CPC for potential visitors that purchase their produce or services. Phil
According to me its normal, there are lots of ups and downs with cpc nowadays and you are lucky that you have ads on non-english site, there was time when ads just wouldn't show up on different languages sites other than english.
The problem is not the country/language, is the niche. Some niches get a lot of traffic but have low commercial intent. The higher the commercial intent, the most you will get per click.