When a rabbit's poop starts looking irregular shaped or soft, there can be several things that can be the cause. If this is happening within a day or two of giving him the handful of alfalfa, then that could be the problem, as he would be getting a bunch of alfalfa all at once, when it's not normally something he gets. Another thing it could be is one or more of the veggies is causing the problem. The only way to solve that would be to cut the veggies out of his diet to see if his poops return to normal. If they do, then you would start reintroducing veggies back one at a time, and when you get to one that causes the weird poops, then you would know what your problem veggie is. But more commonly it is treats or pellets that cause this kind of problem. Since you don't normally feed sugary treats, then the pellets may be causing the problem. You will want to stop treats and also reduce his pellet amount each day. You could maybe go down to 1/3 cup a day and see if his poops go back to normal. If not you could go down to 1/4 cup and see if that works. If reducing pellets doesn't fix the problem, then you may need to try eliminating veggies next, to see if they are the culprit. The benefit of reducing pellets, is that it will also cause him to increase his hay consumption.
Some other things that can cause digestive problems in rabbits are parasites and bacteria. If diet changes don't fix the problem, or if his health gets worse, then parasites or bacteria may be the problem and you should get him to the vet right away, to get some meds.
The peeing could be marking behavior, but a UTI or bladder sludge can also cause a rabbit that is litter box trained, to start having frequent peeing accidents. If you suspect a health problem is the cause, then you would need to take your rabbit in to the vet if it's a UTI. For bladder sludge, you could try cutting out veggies that are high in calcium and oxalic acid to see if it makes a difference with the peeing accidents.
