yellow tips...?

my 8 babies are a week old and i have 8 cfls 1-2 inches away from all of them. i have a second pair of leaves coming in now and the first leaves are beginning to turn yellow on the tips... i heard this was normal but i just need clarification. and i was curious to know why this happens?

well they dont usually die that quickly in my experience,i have 9 2 week old plants and all of the false leafs are still healthy and green,but your right ppl have said its normal in there experience,if the new growth looks healthy then its probably nothing to worry about,,,those leafs your talking about contain what a seedling needs to get started,and once theyve been sucked dry by the plant they die,,,,,,,,,,,,peace