My first instinct is to say no. Usually septoria has a more defined brown circle, light colored center and a little yellowing around it. If this is your only bad leaf I wouldn't worry about it right now, but I try not to spray until I have to. Be sure to keep the bottom leaves clipped up so they don't touch the ground, or get splashed on when it rains. Keep an eye on the plants, unless you are getting humid/wet weather I wouldn't start a chemical attack against it yet. If it starts to get worse let us know.

It really isn't a close enough photo to the spots to tell for sure. The top pic shows the nutrient deficiency issues well but not the spots. It could just as easily be bacterial speck or even some sort of insect pest damage but without a better pic of the spots on one or 2 leaves I can't tell.

Dave

I will post better pictures in few days if it gets worse.

@Dave

any idea what nutrients my tomato is lacking?

Well you have purple stems and leaf tips which usually means phosphorous deficiency. Plus you have some inter veinal chlorosis in several the leaves in the first photo and that is usually magnesium and/or potassium. The link below is a good bookmark for tomato nutrient deficiencies. That way you can compare the actual leaves to the site photos.

Nutrient deficiencies in tomato plants

Dave

But the underside of leaves are still green, even though top are dark green/blue/purple? We had few nights of mid 40oF, could that be the cause of deficiency?

Possibly. Cool temps will slow uptake in very young plants but it doesn't usually affect established plants. Given the size of the leaves in your photo I assume the plants are fairly good size. Just keep an eye on it as it should disappear quickly once the temps remain above 50.

Dave