Knowing when to increase sodium picosulfate dose?

[Chinchichip]

Hi, my son is currently on 3 sachets of movicol and 3ml of sodium picosulfate. I’m now confident knowing when I need to alter his movicol dosage but I’m not sure about the pico dose. I give him the pico before bed, around 7pm and up until a few days ago he was having a bowel movement the next morning after breakfast. He hasn’t managed this the last two mornings and when he does go later in the day it’s indicates that’s he’s struggling to go again (smelly, dark, sticky etc). Should I be increasing the pico so that he goes within those 12 hours? I’m waiting for half term to do another disimpaction as he’s been soiling. Is it ok to wait or should I just do it now? He would have to miss school for it.

Any advice at all will be greatly appreciated. Thanks!