Losing weight too quickly?

I know I've read and heard so much on losing weight too quickly being hard on your body. I have a fairly active job most days and I've increased my activity at home (just helping around the house a lot more).

I got back on MFP and started tracking my calories again and hitting the calorie goals easily (occasionally well under them). However, I was a bit concerned when I stepped on the scale and my weight had dropped 8 pounds in the matter of 3 days. I know my net calories aren't THAT low. My girlfriend and I are doing weigh ins every 3 days, but I cheated this morning and hopped on the scale to see if maybe there was something goofy with it, but I looked down and it read another loss of 1.2 pounds... in a day.

I'm staying well hydrated, usually 10-12 glasses of water a day plus a gatorade. I'm wondering if this is just the affect of the huge change in diet I made ... I used to eat all kinds of junk at work, I would guess daily I was pulling in around 4000 - 4500 calories. So I'm thinking this just may be my body adjusting to the big swing in calories. Should I have gradually stepped down my caloric intake, or was this the right move I just need to give my body the time it needs to adjust?