Yes, stack some more HP. About 3k more and then you'll be fine.
Sorry, but you're water/elec and you still can't do it? D:
First, DON'T attack them all at once if you can.
Isolate one, stun with electro and then shard+electro until it dies.
Shard+Thunderbolt is too risky sometimes and will miss. It's better to just keep rotating shard+electro in tandem.
Oh and if you don't already, USE YOUR F1-8 KEYS! I see some people just NOT take advantage of that godsend and use their mouse to cast shard+electro. The difference in reaction time will literally make a huge gap in success or not.