Hello, my husband and I refinished our hardwood floors. We rented a belt sander & edger using 20, 36, 60 & 80 grit papers. Then went over with a vibrating sander using 100 & 120 grit papers to finish. We swept & vacuumed the floors last night. Today I started staining them. This is where the problem begins. After the first coat started to dry I could see spots all over the two rooms I stained but there were no visible spots on the bare wood floor. I’m not sure what the problem is and how I can fix it. I did wash the walls last night and had water drip on the floor so I’m thinking this could possibly be the culprit but I’m just not sure. Any help would be appreciated. I’d like to attach a picture but I’m not sure how I can do that.

Water is the problem. You will get dark spots from water wetting the bare wood before staining. You will get white looking spots on floors that have been stained when water drips on the stained floor.
It is important to keep water away from bare wood when it is going to be finished.

Will sanding and staining again remove those spots? Do I need to do anything else? Thanks!

We ended up sanding the floor again after the window cleaners spotted the floor with water. They said that they would not spill.
You may be OK with rubbing firmly with #2 steel wool, but do not use water-based finish after steel wool.
You ought to polish with steel wool before your first coat of finish, anyway. Just try a small spot to see if this works. It depends on the color of the stain you used.