I've had my ball python for a year and a half now and things have been fine, hes on a dark wood bark substrate and i've been feeding him mice once a week of approximately the same size as his thickest point, hes been healthy up until now but in te past couple of days whenever i've been trying to handle him he has been hissing at me, at first I thought this was because he was hungry so I fed him, left him 2 days for digestion to start etc but he continued, so I tried lowering his heatmats etc in case he was overheating with all the hot weather we've been having recently but that hasn't helped, he also looks abit grey and msity as he normally does before his malting period, is this the cause or is he ill? any suggestions? thanks Andy