Using any thing like that on seedlings that young would probably end badly.

+1 to what Ga said,... spray your soil with neem, there's a good possibility it's fungus gnats, a topical neem application that's watered in will cure them in 2-3 weeks,.... use the neem every 2nd or 3rd watering to prevent oil build up on the roots choking them, and SPRAY the topsoil before watering, do NOT water neem mixture directly into the soil!

This method has halted fungus gnats, and a potential root aphid infestation in their tracks after several months of NOT applying Neem on a biweekly basis. (done as an experiment to see how long it would take for signs of bugs to show,... now I'm back to my normal routine! ) Not to mention, I've seen not hide nor hair of a spider mite in my grow in over a year!!!!

Neem is also known to systemically knock down PM in plants,.... perhaps its a coincidence I've never seen PM in my room?