Moms with tots please chime in

My 2 year old has me totally frustrated. He has been so mean lately with his brother. i don't know if I'm doing something wrong or if it's just a phase. A crawled over to the tub yesterday while Jace (my 2yo) was in the tub. J had little bottles filled with water along the tub lined up. He likes filling them and lining them up. Apparently A must have grabbed one or something and J got mad and started pounding A in the face with a bottle. I didn't see this happen b/c my parents were the ones giving him a tub b/c the dog peed on J's head. The boys usually take tubs together and have fun. Later A touched one of J toys and J pushed A over from a sitting position onto his back. My dad managed to catch A before he hit his head on the floor. Then today J was on his toddler sofa we bought him a while back and A crawled onto it to sit with J but J kicked him off. I don't know why my normally sweet boy is being so mean. He has started slapping me when he gets upset with me, which I don't tolerate and he gets an immediate time out. He's not always mean with his brother. There are days where they get along beautifully. They will crawl after each other and giggle and laugh together and alternate chasing each other. J will sometimes share his sippy cup of milk without prompting wih A. He shares food sometimes, toys etc. on several occasions J has shared his lovey with A when A is sad or crying a lot which is incredibly sweet. I never make him share his lovey b/c I believe that it's something personal for J. If A takes it away from J I make sure to give it back promptly. J will give a ball to A outside for A to play with, he'll wisper and say " shhh Avery is sleeping" when A naps, he asks for A in the morning when he first wakes up, etc. am I over thinking this? Am I doing something wrong? Is my son acting out or some sort of sociopath? I give J one on one time when A is napping and I have dh or someone else play with A so I can play with J one on one. I take them to the park and go down the slide with both of them each taking turns. I feed J sometimes like I do for A . I share some of A's snack with J so he doesn't get jealous. I kiss both of them and praise both of hem. I don't know what else to do. I have J help me unload the dishwasher which he loves, helps me stir stuff in the pan when I cook, helps me with the windex, I let him taste stuff with me when I cook, he helps Maputo stuff away or into the trash, we read books together, we dance to music together, he does stuff his brother doesn't get to. He went to my parents house for 2 days without his brother to get singled out attention and unlimited fun, four wheeler rides, grandpa time, etc which he loves, then I come up with A for a day or two so we're all together. I'm sorry this is so long. Is there something I'm missing or not seeing? I am open to anything right now! He's not normally like this. ************** no paragraphs due to iPad being dumb*************