First post, so I'm hoping I don't make too many errors in etiquette.

I brought my house last year and as part of annual checking figured I'd make sure all the sprinklers that the prior owner had had installed were working still (and pointing in the right directions).

House is in El Cerrito (Northern CA) has three sprinkler zones (quite frankly I think the setup is wrong, but right now is NOT the time for me to be trying to change it all around).

Zone one has a bunch of popups
Zone two has four pop-ups and two impacts, one of the impacts is a SuperJet (at least that's what it says on top of the impact head) the other claims to be a Toro (and seems to have a designation K05?)
Zone three has 3 impacts all Toro (D04 apparently) and three popups.

The issue is in Zone 2, the Toro Impact doesn't appear to be getting enough pressure to work properly (it turns quite slowly and doesn't have the pressure to trip the release so that it turns back around, so it gets to the "end point" and then stays there not turning).

I've not found anywhere with any obvious "puddling" so I don't believe it's an underground leak (but may be wrong), and I'm vaguely thinking maybe the filter needs cleaning? Does anyone have any ideas for getting the head out of the sprinkler to check it, I know that Rainbird makes a sprinkler Wrench that would seem to go into the guts of the impact sprinkler, but I'm not sure if the wrench size is universal or specific to rainbird heads.

Any advice?