I GAVE A LETTER OF COMPLAINT TO MY LANDLORD AND NOW THEY ARE PICKING ON ME WHAT CAN I DO?

I LIVE IN WHITTIER CA AND I GAVE THE MANAGEMENT A LETTER OF COMPLAINT AND NOW I GET A "3 DAY NOTICE TO PERFORM COVENANTS OR CONDITIONS OF LEASE OR QUIT" WHICH THEY ARE TALKING ABOUT A BBQ PIT I HAD OUT THERE FOR MORE THEN 5 MOTHS AND I KNOW THEY HAVE SEEN BEFORE BUT NOW ALL OF A SUDDEN THEY WANT TO COMPLAIN I HAVE PROOF THAT THEY HAVE SEEN MY BBQ PIT AND NEVER SAID ANY THING SINCE THE FIRST NOTICE. I READ IN CIVIL CODE 1942.5 THEY CAN NOT RETALIATE AGAINST ME, BUT I DONT KNOW WHAT TO DO??? OR WHERE TO START???