Hello all! First post but not new to the forum.
I got my pied ball last January, he hatched September of 2018. This is my first ball python and I've learned so much in a year. One thing I've had problems with on and off is feeding. I feed frozen/thawed. The first 3 months (Jan-Mar) were problem-free. As soon as a rat entered the enclosure it was game over, always. Perfect strike and coil, immediately followed by eating the rat in less than 10 minutes. In April came the first feeding strike. I would wiggle the rat, he'd come smell it and go back to his hide. I would leave the rat in his enclosure overnight and it would still be there in the morning. This went on for a month, before then he ate again.
We were back on track in May-mid November. Highest weight being 550g. He has been off feed since the first week of December and is losing weight rather quickly. I don't have a current weight but I'm starting to be able to see his spine and he is noticeably getting thin.
He seems to be afraid of bigger prey so I've been stuck feeding him 50-60g rats. He immediately backs away from larger prey. I've been feeding every 5 days since he's only eating smaller meals.
Currently, I'm waiting for my T8 from AP cages. The tank he is in now is small for his size.
Husbandry has always been spot on. Humidity 60%, hot hide 90F, cold hide and ambient temp 75F.
I had a stool sample done in November and everything came back normal.

Any suggestions will be greatly appreciated.
What can I do differently?
Thanks for the help everyone