weight gain diet plan

hey.. i have posted here several times and have always tried to help when i could and have always been helped. great site.. i am confused on my weightloss lately.. i have been preparing for a cycle all winter and had a great plan going.. i am eating relatively clean..(4500 a day)... had gained from 198 to 212 with 5 a week workouts... heavy mostly 5x5.. also drinking about 1 gallon of water a day.. had something come up that i was not able to work out but 2 times and my eating went to about 2800 to 3200 a day.. within about 2 weeks i am down to 199 and muscle tone is going fast.. what is this... help please.. i am back now starting monday on full diet and workouts again... took a while to get it and now 2 weeks to lose it.. i want it back fast.. summer is here and i want to be at that weight and muscle size back pre cycle.... any suggestions on what happened and how to get back QUICKLY... thanks... btw i am 6'1... great shape, no med. problems, had a few sleepless nights though...