WELCOME and HELLO !
It sounds normal, according to guinea lynx below. Just keep an eye on it, but if it isn't gritty or sludge like, it's normal. Their system is probably just adjusting to the new and better healthy diet of fresh veggies, however it might be that they are getting too much calcium in their diet, not sure !
Have you had a chance to read and look at Ly& Pigs nutrition charts, poisonous plants list and sample daily diet menus ? Ly is our Adm/Mod/Nutrition Expert on here. Here it is below:
https://www.guineapigcages.com/forum/diet-nutrition/24770-sample-veggie-menus.html
NORMAL:
Urine may be clear to cloudy in color. Calcium compounds in the urine cause this cloudiness. Normal urine is
not gritty in texture. Dried urine may leave powdery white calcium compounds. Very young guinea pigs often have an orange or brown tint to their urine. Urine sometimes changes to an orange color on standing (this may be the oxidation of porphyrins in the urine).
NOT NORMAL:
Gritty compounds: may indicate sludge in the bladder. Strong smelling urine may be a sign of dehydration or infection. The gritty deposits are sometimes called sludge, which feels coarse and sandy. Powdery deposits are normal. Rub the deposits between your fingers to determine if they are powdery or gritty.
Blood in urine is not normal and may be due to a urinary tract infection, bladder stones, or (in females) reproductive problems like pyometra (an infection of the lining of the uterus).
Incontinence is not normal. Your guinea pig should be relatively dry. If its fur is constantly wet and/or there is an odor, be sure to have your pet checked out for a urinary tract infection or other problem.
Hope I have been helpful ! Kudos to you too, for choosing to adopt-Yipee !