Why have my basketball skills deteriorated?

Practice again man. if you have body changes specially your height, this is your chance to move to another position and starting doing basics again. Work in the key and if you really really want to shoot jump shots then go for it, it will take time but you can do it. IF YOU REALLY WANT IT. good luck man. If you work in the key, practice more middle jumpers instead of long ones, good luck. Just keep playing. sometimes there are just times like these its normal, just get back on track and play more