Trouble during flowering.

I'm growing an autoflower in FFOF using RO water. I'm getting these spots on the upper leaves during flowering. The bottom leaves are not exhibiting the same spots. I've been feeding primarily CalMag and Bloom nutrients the last few weeks while in flower. I've also been keeping PPM's per gallon of water around 550 so I don't burn them. I'm not sure if this is being caused by overfeeding them or a deficiency. From what I've read, it seems calcium necrosis. As of now, I just want to get her over the finish line. Any insight would be appreciated.

How's your PH?

RO water.Needs more Ca.But can also be a K deficiency.Overwater ,low ph also can look like that.

Thanks for the replies. I'm feeding about 3ml of CalMag and 2ml of GH Bloom per gallon of water. Growing in a 3 gallon fabric pot with a Spider Farmer SF-2000 Led Grow Light. I'm fairly certain it's not insects because I'm growing in a grow tent in the closet of a spare bedroom. I strongly suspect that I'm either under or over-feeding the plant but I don't know which one so I don't want to compound the problem by doing the wrong thing. Trying to figure out what is going on is confusing because so many things look so similar.

You forgot ph..

Give it way more Bloom, like 5ml per gallon and in a couple weeks when flowers get bigger, 7.5ml or even 10ml if she responds well.