ok-- need to know-- what kind of soil & nutes? How often do you water & with what kind of water?
Do you check the pH when you water?
It is not the lights- it is either a lack of P-K or a nutrient lock-up from a pH problem or over feeding...
MANY people use T5's (IMO best bet) For vegging-- and many use MH religiously (I personally did not like them- and switched after a year of weaker than usual grows- but fixtures that can use a wide-spectrum bulb work well..NOT single spectrums!)...
as long as you are keeping the room temps even and fans blowing the air around-- heat is not the issue... the damage from lights would be the tops of the plants, not around the edges.... and heat would be the whole leaf and look dehydrated...
More info plz-- then can help you get this straightened out...
in the meantime-- flush them with some bottled (filterd) water.... and make SURE there is adequate drainage in the bottoms of those cups!!!