I am wondering as catlover is, if Ollie sprayed and Gracie can still smell it, setting her off.
I HIGHLY recommend spaying ASAP because I think that may be a big part of the issue. I had Sweet Pea as a foster, now adopted by me, for four months while she was raising her kittens before she was spayed. She was moody, and would even hiss and attack her kittens, once she was spayed, it stopped.
You say you love your kitties, IMHO, part of loving your kitties is to ensure they have the healthiest diet possible. Cats who are not on canned food for the majority of their meals can be chronically dehydrated, making them feel a bit lethargic and not their best. Cats who eat substandard food can't possibly be at the peak of health, period. I can tell you I felt the same way about food as you do, until I saw the difference a quality canned food, now raw, no kibble made in Puddles. I would trust sugarcatmom before my vet for many, many things, including nutrition advice. She is an absolute guru.
Here is a link on cat nutrition, it is a bit long but very, very informative: