I'm not sure if that's foil or mylar but if its foil than you need to remove it, foil will raise your temps. also when you water always water the entire pot evenly so that there are no dry patches and allow a little run off. when you want to know when to water again just do a weight test if it feels fairly light in weight than water it.
The reason to cut back on the nutes is because your plant needs all factors of growth working together evenly(water,C02,temps,nutrients,etc.) to produce its maximum growth potential the plant will only take what it needs when it comes to nutrition EXAMPLE if you increase only one factor essentially will not produce better results all factors of growth must come into consideration for max yields and potency which is the common goal for all of us. I highly recommend reading the article to get a better understanding on the process
LESS IS MORE AND KNOWLEDGE IS POWER!!!