You need to be adding calmag plus if you are using distilled water. That doesn't look like a 'classic' calcium deficiency to me, but there's no getting around the fact that you need plenty of Calcium that is missing from distilled water.
Those spots actually resemble a K def. Something weird is going on with your nutrients. But start with the CalMag Plus, and look at options for hydroponic-specific fertilizers while you're at the shop.
Next time you buy nutes, I VERY highly recommend the Canna Aqua A+B, whcih I run in hydroton with plain TAP water haha and is VERY VERY forgiving. I don't even have to play with the pH because it comes buffered.