Switching from alfalfa pellets to timothy pellets

I recently noticed Belle's urine has been a milky yellow color and was reading up on if this was something to be concerned about. After doing some research I came to the conclusion that she has been getting to much calcium in her diet from some of the veggies I was feeding her so I started feeding less of those and watching when I feed them.
I also noticed a couple of days ago that she is on alfalfa pellets and not timothy. I went to buy some and the bin was empty so the associate filled it back up so i decided to read the label on the back to see the fiber amount and alfalfa was the first ingredient! The owner told me that the pellets in their bin that they sell for $1 per scoop was timothy. The pet store I buy my two rabbits pellets from is the same pet store I bought Sir William from that knows nothing about him. Go figure.
So after all that rambling my question is since I am not switching the brand of rabbit food but I am switching from alfalfa ti timothy should I still serve them a mixture of the two and introduce slowly? They were originally on the same brand rabbit food but timothy based and was suddenly switched unknowingly when I started buying out of the bins.

Do you think it would be okay to do half and half over a two week period? I don't have much of the alfalfa left and I didn't plan on going back to that pet store. I will if I have to it's just if rather not deal with that store anymore.

A two week period is fine for transitioning, though it would be better to start 80%-20% and gradually increase the timothy and lower the alfafa, rather than going straight 50%-50% all through.

A note on urine, milky urine is perfectly normal and healthy. It shows she is excreting the calcium in her diet well. If it was totally clear something is wrong! What too much calcium actually produces is SLUDGEY urine, which is when a significant amount of sludgey sand/clay-like solids are present in her urine. If it's just milky liquid, you have nothing to worry about.

Thank you for clearing that up! That makes me feel better knowing that it's okay if it's milky! Definitely not sludge. I would have made an emergency trip to the vet if I saw that. That would freak me out! I've been doing 1/3 timothy and 2/3 alfalfa. I SHOULD have enough to that for a week and bump it up for the next week and hopefully do one last mix. Thank you for sharing!