ah ya you did clearly state that info lol
go easy...im only trying to help.. and where all pot head here lol
im not sure how much help I can be but I will speak openly and maybe something will ring a bell thru dialog ... if its water only and no fertilizers and the leaves are that dark green I have to guess the soil might be your issue
does that soil have the time released nutes in it? does it say organic by chance? does it say feeds for X amount of time on the bag?
if I had to take a total guess as to where I might start if it was me... and this is just me taking a shot in the dark
I might consider the soil to be heavy on N fertilizer... if its time released food youll be hard pressed trying to flush.. but id like to see my leaves not as dark green as those
the speckles could be (as in might) calcium deficiency if they starting from the bottom and working its way up... if its on the tops first it could be micro nute related or ph issues
ive not seen a whole plant pic so I don't know how wide spread the issue is..if its a few leaves id ignore it... if its all over and getting worse I might try flushing
if (IF) I happened to guess right the issue is how do you flush out the N and add calcium... since most calcium sources of fertilizer come from calcium nitrate
theres a lot of speculation in this paragraph, but im trying... so don't hold my feet to the fire
whole plant pics would help a lot