IMO P is not needed in excess amounts in container gardening whether in flower or not...tissue sample analysis shows it is least used of the macros with calcium being needed up to 3 x's more than P...The use of high P foods is a bleed over from Agriculture to gardening to indoor container gardening...as P is readily leeched off from soil and binds quickly with soil farmers of old upped the P during fruiting to combat it and it worked...only later to discover that the soil was now P laden and other measures were now required to "heal" the soil...they since have employed better applications of P freers in their formulations...however this does not occur in containers so it actually inhibits growth ...
Now a P and K spike at the end of flower may increase resin production due to the stress factor but IMO much more important is a cal and sulfur boost mid flower on as sulfur is required for synthase production which produces the desired cannabinoids
as for the pulling away...do not let them dry out...use a fast draining high perilite etc mix so overwatering is damn near impossible and keep them wet
And cn with your gait you should be a soil/snow expert