Blue explosions after blue pack.

I was hopping around in a coves with extra damage minus regen. Last few pack I hopped into and 2 shot with ice crash was about 15 blue crabs. After 2 hits I was about to hop away to the next pack and they all turned into little blue balls very quickly and exploded. As you can see I am now in standard but are there any visual ques to this affix? or whatever it is. Am I now just going to be mentally scarred and reading ever blue pack slowing clear speed to a crawl. I've seen mobs detonate but there is usually a delay. I've seen detonate dead but this was different.

It is a bloodlines mod, there r many different. Of this particular type there 3, fire, ice and lighting.

http://pathofexile.gamepedia.com/Monster_affixes#Bloodline_affixes

Oh wow didn't realize there where that many. Was my stupidity anyways thinking I was invincible. I am used to getting instantly killed in tempest anyways. Thank you for info. Have to watch out for magenta text mobs.