ZOMG , it is not working , stop it right away!!! 15 kg max loss in 3 days , in 30 days you will be down to 0kg 1RM and then you will go negative!!!
OR , it could be just a bad day , maybe you were a bit sick and didn't know it , it could be million things.
My point raptor is that you should not worry about 1 bad training day , especially the 1st one after a drastic change on your long term steady diet.
Give yourself some time to adapt to the new plan, see how it goes ( weight , bf% , abs stength , rel strength ), reevaluate.