HELP! White spots/leaf damage on tomato seedlings
 

Hi, I need help diagnosing an issue affecting some Tappy's Heritage tomato seedlings I transplanted on 4/3. A few days ago, I noticed white spots and some leaf damage on some of their leaves.

Planted these from seed around the start of March in an organic seedling mix from Scotts or one of the other big soil/fertilizer producers. They've been on a windowsill that gets 6-8 hours of direct sunlight and good indirect light the rest of the day. Our apartment tends to be pretty dry.

Was thinking this might be a case of powdery mildew...? But not sure. I have little experience diagnosing plant issues and am just going off the pics in troubleshooting guides some of the university extensions put out.

Burn?

Hmmm any sign of insects? Spider mites, other houseplants? Have they been outside at all?
KarenO

What does the underside of the leaves look like?

Underside of the leaves look clean. We have noticed some very small/fine webbing (like a tiny spiderweb) on one or two of these, either on the top of the leaf or connecting the leaf to the stem.

Similarly, I did notice similar webbing on the top of the leaf of a Colocasia that's sitting near these. They haven't been outside yet. On a sunny window ledge in a pretty dry/well-ventilated apartment.

Thought so, spider mites. Spray with safers soap.
KarenO

Thanks for the advice. Will neem oil work as well? Have some handy.

yes, its would, a bit harsh for seedlings so caution
KarenO