Little Brown spots appearing over last week

Checked my plants today and noticed this:



What is causing these brown spots. They appear to show up in the last week. I give them 1.5 litters of water every 2 days. Alternate from Feeding and plain water.

Should I cut down the feeding even more? There are still at least 3 weeks left in grow.

Edit: I use fox farms Big bloom, 4 tablespoons per gallon (as per bottle)

Please help.

im haveing same issue but much earlyer and its not mag def or potash

It needs potassium.

Do you have a source of calcium?

Well all I been using is fox farm soil and then grow big, then big bloom when the autos went to flowering.

Now big bloom is 0.01/0.3/0.7
And grow big is 6/4/4

Can I feed it some grow big for the potassium and fix the problem, or will it just cause more


None of local nurseries have anything thats just potassium suppliment (lack of better words).

Take a few days to order anything as well.

Suggestions for course of action?

Thats a Ca deficiency.

Feed some, or more calmag.

My widows chew through Ca late in flower, i add 3 ml/l calmag on top of my tap water or they'll look just like that.