Can someone help me?

These guys are 2.5 weeks old. They are Kellogg's Breakfast Tomatoes. I started the seedlings in peat pellets for one week and then transferred to pots with Organic Seed Starting Jiffy Mix. They are under a window and get sunlight for about 6 hours a day. I also have two 75-watt GE Reveal Halogen lights on them for 13-14 hours a day. They get a good 8 hours of dark. House temp is at 70 degrees. I water about every 60 hours after the pots have become completely dry.

In the last several days, leaves have begun to curl and tips have become necrotic. It is hard to tell, but there is some purple spotting forming under the leaves. Two of the four plants also have bumps near the base of the stem. (There are some specs of dirt on some leaves, not aphids, sorry).

I am also growing Red Currant and Cherokee Purple plants of the same age and set-up that are exhibiting NO signs or issues. I have used this same set-up for the past three years and have never had this issue before.

I read somewhere that this could be temperature or even a potassium deficiency but wanted some expert opinion before I tried anything.

Thank you for any help you can provide and a happy growing season to you all!

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