pH is 5.5 but i have nutrients deficiency. Can it be the cold?

Hello, Try and keep your water around 18-21'C/65-68F. Too clod and your plant will struggle to absorb nutrients, too hot and the plant struggles to absorb oxygen. May be the other way around but you get what I am saying I hope. Not sure but that does look like a fungus rather than calcium, She is in flowering now and as you probably know, she needs less nitrogen at this stage. However the plant still needs it and will shed leaves when nitrogen becomes limited. Make sure you are keeping your pH correct and not overfeeding, autos can be temperamental when it comes to nutrient needs. I hope this helps, good luck and happy growing