Ceanothus are not a long lived shrub Guest. It could be age. Lack of sufficient water and feeding. Unfavourable placing. We lost one due to windrock after a severe gale. If you cut back into to them too far they may sulk and produce brown patches. They are a shrub that looks marvellous for a while then shades off into frumpy middle age. Not a shrub that you can prune back to rejuvenate or it will die on you.