Yes. I would be concerned. I would remove the plants and put them in new soil.

Assuming that you know for sure that it is old lead-based paint, then yes, I too would transplant to new soil. But it has been many years (early 70's) since lead based paint was even available so it may not be a problem.

If it is lead based a greater danger comes from breathing the dust.

Dave

Lead based paints have been forbidden since the 1970's, so most outside paints have been replaced by now. The major problem is inside the house where the paint is more protected and does not peel off as it does outside. Even more so that breathing the dust (the only time you would need worry about that is when you are sanding paint) is ingesting, eating, some paint chips containing lead. That is the most common way children get lead into their systems. Most of us with older homes most likely have soil around the house contaminated with lead, for that peeling paint, but if your house was built after the 1970's you will have no concern about that, unless an older house was there before.
What you need to know is how old is the paint that peeled off is and how old the house is (keeping in mind that for someone born in 1990 a house built in the 1970's is old) and the chance that some paint manufactured before 1970 is to be still on that house.

Yes, but even today's modern paints are not lead free, they just have less lead in them than the older paints.